定语从句跟在名词（先行词）后面对其修饰限定，分限制性与非限制性两类：前者是认定先行词身份的必要信息，后者用逗号隔开、只作补充说明。它是真题里出现频率最高的从句类型之一，也是阅读断句的第一道坎。
英语四级真题里的定语从句共 2728 处实例，本页按 2 个子类型分节，精选 50 句真题例句（出自 19 套真题卷，句长 11–54 词）。 每节先给该子类型的实例计数与常见引导词分布，再逐句给出例句：高亮定语从句在原句中的位置，标注引导词、嵌套父与所在层级，附中文翻译、逐句解析与出处试卷； 点句卡末尾的「本句详情」可看结构树逐层拆解、成分与时态标注、考点讲解与真题高频词。
识别要点 看名词后的 that / which / who / whose / where / when：有逗号是非限制性（可先整段跳过抓主干），无逗号是限制性；再判断引导词在从句内充当的成分，翻译时据此决定前置还是拆句。
本页精选的 50 句真题例句已由懒笔记排版为 A4 打印版 PDF，可免费下载，PDF 内的真题出处链接均可点击。
常见引导词： that 854 · 零引导 680 · who 545 · which 99 · where 88 · when 22 · whose 9 · why 9
Some researchers maintain that there is another type of disgust, called moral disgust, that protects us from engaging in activities that can be perceived as morally wrong.
一些研究人员认为，还存在另一种类型的厌恶感，即道德厌恶感，它能防止我们参与那些可能被视为道德上错误的活动。
该定语从句紧跟“another type of disgust”，限定是哪一种厌恶：它能够保护我们免于从事某些活动。“that”在从句中作主语，对应“that protects...”；没有逗号，属于限制性定语从句。
But in a phone interview, the only thing you have to go on is what you say and how you say it.
但在电话面试中，你唯一能凭借的就是你说了什么，以及你是怎么说的。
该分句紧跟并限制先行词"thing"，可还原为"the only thing that/which you have to go on"。省略的关系词在从句中充当介词"on"的宾语，因此这是零引导的限制性定语从句；从句的evidence只应覆盖从句本身，无须包含先行词。
This type of study can't say exactly what kind of exercise is best, or how much is needed—only a study that has a placebo(安慰剂) group and tracks people going forward can do that, said Keith Fargo, director of scientific programs and outreach at the non-profit Alzheimer's Association.
非营利组织阿尔茨海默病协会科学项目与推广部主任基思·法戈表示，这类研究无法确切说明哪种运动最好，或需要进行多少运动；只有设置安慰剂组并对参与者进行前瞻性跟踪的研究才能回答这些问题。
该从句紧跟名词“study”并限定研究的类型。关系词“that”在从句中作主语，后面连接并列谓语“has”和“tracks”；删除后研究所指范围会扩大，因此属于限制性定语从句。
It is a term most parents use when talking to children.
这是大多数父母和孩子交谈时都会使用的一个词。
该分句修饰并限定先行词"term"。关系词被省略，完整形式可理解为"most parents use that/which when talking to children"；省略的关系词在"use"后作宾语。
He recommends practicing answers to questions you know will be asked ahead of time in order to be clear on what you're going to say.
他建议提前练习那些你知道面试时一定会被问到的问题，以便明确自己要说些什么。
该限制性定语从句紧跟先行词“questions”，限定所练习的是哪些问题。可补出关系代词“that/which”：questions that/which you know will be asked ahead of time。关系代词在更深层的内容分句中充当“will be asked”的主语；“you know”是插入于关系结构内部的主句，其后的内容为关系代词所承担主语位置的命题，而不是一个可以单独切出的、缺少主语的宾语从句节点。
Most of the time, this assumption is accurate: someone you think of as a friend will usually consider you a friend too.
大多数时候，这种假设是准确的：你认为是朋友的人，通常也会把你当作朋友。
该从句紧跟并限定先行词 "someone"，完整形式可理解为 "whom/that you think of as a friend"。被省略的关系词在 "think of" 后充当宾语，"as a friend" 是对该宾语身份的说明；没有逗号隔开，因此属于限制性定语从句。
This is the first trial that demonstrates that there is something about highly processed foods—independent of those nutrients—that causes people to overeat.
这是首项试验证明，除了其中所含的营养成分之外，高度加工食品本身还存在某种会导致人们吃得过多的因素。
该从句的先行词是 "something"；关系代词 "that" 在从句内作 "causes" 的主语。该从句限定这种与高度加工食品有关的“某种因素”具有使人过量进食的作用。
People we want to have detailed information about are keen to know about us.
我们希望详细了解其信息的人，也很想了解我们。
这是修饰并限定先行词"People"的限制性定语从句。关系词被省略，介词"about"后本应有与People对应的宾语空位，完整理解相当于"People whom we want to have detailed information about"。
Those that believed they fell claimed that the capitalists squeezed every ounce of surplus they could from the working class.
那些相信自己已经倒下的人声称，资本家从工人阶级身上榨取了他们所能榨取的一切剩余价值。
“they could”无逗号地跟在“every ounce of surplus”之后，限定资本家能够榨取的剩余价值数量。关系代词在从句中本应充当省略动词“squeeze”的宾语，表层同时省略了宾语关系词和情态动词“could”后的重复实义动词，可还原为“that they could squeeze”。
Playing the piano is among the things the world's oldest person believes has contributed to her long life.
弹钢琴是世界上最长寿的人认为有助于她长寿的事情之一。
限制性定语从句修饰先行词 "things"，关系代词作从句内嵌套的宾语从句的主语被省略（零引导）。从句结构是 "the world's oldest person believes (that) [关系词] has contributed to her long life"，其中 believes 后省略 that，其宾语从句的主语是省略的关系词（指代 things 中的某项）。这是典型的双层嵌套：定语从句内嵌宾语从句，且关系词在宾语从句中作主语。
One benefit of this change is that students will not fall victim to the "summer slide," or the well-documented phenomenon where students forget some of the knowledge they have acquired when too much time is taken off from school.
这一变化的一个好处是，学生不会成为“暑期滑坡”的受害者，或者说，不会成为那种有充分记载的现象的受害者，即当学生过多时间离开学校时，他们会忘记一些已学到的知识。
where 引导限制性定语从句,修饰先行词 phenomenon,在从句中充当地点状语(抽象地点)。从句无逗号与先行词分隔,且不可删去,符合限制性定语从句特征。从句内部包含定语从句 "they have acquired" 和状语从句 "when too much time is taken off from school"。
"Every motorist sits in the comfort of their car, but they don't give any consideration to the price their comfort has for the environment and consequently for themselves," says Orion.
"每位驾车者都坐在他们汽车的舒适环境中，但他们没有考虑到这种舒适给环境以及因此给他们自己带来的代价，" Orion说。
修饰先行词"the price"的限制性定语从句,关系代词that/which作"has"的宾语被省略。完整结构为"the price [that/which] their comfort has for...",关系词代表"the price"在从句中作宾语。"for the environment and consequently for themselves"是并列介词短语作状语。
The city has provided 2,200 incentives to lower-income residents that represent 68% of the program funding.
该市已向低收入居民提供了2,200项激励措施，这些措施占项目资金的68%。
该从句由关系词 "that" 引导，关系词在从句中作主语，谓语为 "represent"。它限制性修饰前面的 "incentives"，说明这些激励措施代表项目资金的 68%；"to lower-income residents" 是动词短语中的受益对象成分，插在先行词与定语从句之间。
Based on the participants' self-reported symptoms, withdrawal symptoms were significantly more intense between the second and fifth days after attempting to reduce junk-food consumption, which parallels the time span people live through during drug withdrawal.
根据参与者自我报告的症状，在尝试减少垃圾食品摄入后的第2至第5天，戒断症状明显更为强烈，这与人们经历药物戒断时所持续的时间段相当。
“people live through during drug withdrawal”紧跟在先行词“the time span”之后，可还原为“the time span that people live through during drug withdrawal”。关系词被省略，并在从句中充当“live through”的宾语，因此是限制性定语从句；其完整证据还必须包含内部的时间介词短语。
Remind consumers of the wide connections it can help to build.
提醒消费者，它能够帮助建立广泛的联系。
这是限制性定语从句，修饰先行词"connections"。关系代词被省略，关系词在从句中充当"build"的宾语，完整形式可理解为"connections that it can help to build"；"it"是从句主语，"can help to build"是谓语结构。
The primitive tools early humans used tell a lot about their life, but my favorite is the coin collection.
早期人类使用的简陋工具能够充分反映他们的生活，但我最喜欢的是钱币收藏。
这是限制性定语从句，修饰先行词“tools”。关系词被省略，完整形式可理解为“early humans used that/which”，其中关系词在从句中充当“used”的宾语。
M: Well, I downloaded an APP that recorded how much time I spent on my phone.
M：嗯，我下载了一个能记录我花在手机上的时间的应用。
该从句紧跟名词短语 "an APP"，限定说明是哪一个 APP。关系词 "that" 在从句中作主语，"recorded" 的宾语是后面的间接疑问从句；没有逗号，属于限制性定语从句。
The findings may also shed light on the barriers people face when changing eating habits—barriers that may play a role in people dropping out of treatments, she said.
她说，研究结果还可能揭示人们在改变饮食习惯时所面临的障碍——这些障碍可能会导致人们退出治疗。
该从句修饰先行词 "the barriers"，可补出关系代词为 "that/which"，其在 "people face" 中充当宾语。由于没有逗号，该从句限制并具体说明人们所面对的障碍。
However, there are people who are permanently plagued by a massive amount of self-doubt despite delivering a good performance.
然而，有些人尽管表现出色，却始终饱受大量自我怀疑的困扰。
该从句紧跟先行词 "people"，没有逗号，用来限定“哪些人”。关系词 "who" 在从句中作主语，后面的谓语是 "are permanently plagued"，因此属于限制性定语从句；句末的 "despite delivering a good performance" 是该从句中的让步介词短语。
Wide awake at 3:30 am with our nine-year-old daughter on our lodge balcony, I stared for hours at the most incredible night sky I've ever seen before the dawn slowly started to rub out the stars on the horizon and the multiple shooting stars faded away.
凌晨三点半，我和九岁的女儿在小屋的阳台上毫无睡意。我凝望了几个小时那片我见过的最令人惊叹的夜空，直到黎明缓缓抹去地平线上的星辰，几颗流星也渐渐消逝。
“I've ever seen”修饰先行词“the most incredible night sky”，实际可理解为“the most incredible night sky that I've ever seen”。关系词在从句中作“seen”的宾语，因此可以省略；该从句没有逗号，属于限制性定语从句。
"The degree to which we find these flavors bitter is, in part, determined by your genes."
我们觉得这些味道有多苦，部分取决于你的基因。
这是限制性定语从句，修饰先行词 "degree"，没有逗号，限定的是苦味被感知的程度。关系结构是 "to which"，其中 "which" 作介词 "to" 的宾语；从句内部的基本结构是 "we find these flavors bitter"，即“我们发现这些味道是苦的”。
Those that believed the standards of living rose claimed that the environment was consumer-friendly, with more and more goods available to the working class every year.
那些认为生活水平提高了的人声称，当时的环境有利于消费者，每年都有越来越多的商品面向工人阶级供应。
该从句紧跟在先行词 "Those" 后面，无逗号，用于限定哪些人相信某件事；关系词 "that" 在从句中作 "believed" 的主语，因此是限制性定语从句。
"Chances are if a candidate is participating in a phone interview, this is the first time they have talked with the company, and the first call isn't the appropriate time to talk about 'what's in it for you,'" says Justina Strnad, the Talent Acquisition Manager for Shiftgig.
Shiftgig人才招聘经理Justina Strnad说：“如果候选人正在参加电话面试，很可能这是他们第一次与公司交谈，而第一次通话并不是谈论‘这对你有什么好处’的合适时机。”
该从句限制并说明先行词“the first time”，表示他们与这家公司交谈的那一次经历。关系词在从句中承担时间状语功能，但未显式出现，因此记录为零引导的限制性定语从句。
In addition, people who were more sensitive to quinine's bitter flavors and those found in green vegetables tended to avoid coffee.
此外，对奎宁的苦味以及绿叶蔬菜中的苦味更敏感的人，往往会避免饮用咖啡。
该从句紧跟在名词"people"之后，没有逗号，限定具体是哪一类人。关系词"who"在从句中充当主语，谓语为"were"，因此属于限制性定语从句。
"We're honored to be a part of transforming the way Denver wants to move around," said Grace Rink, Denver's chief climate officer.
“我们很荣幸能够参与改变丹佛市民出行的方式。”丹佛市首席气候官格蕾丝·林克说。
该结构修饰先行词“the way”，表示丹佛想要如何出行。“the way”后没有显式关系词，可理解为省略了表示方式的关系成分；从句内部主干是“Denver wants to move around”，其中关系成分在语义上作方式状语。
常见引导词： which 271 · who 84 · where 37 · when 7 · whose 7 · as 4 · whom 4 · 其他 1
The most common question I'm asked always centers around how to get started in user experience design, to which my response is always that nothing can substitute real-world experience.
我被问到的最常见问题总是围绕如何开始用户体验设计，对此我的回答总是没有什么能替代真实世界的经验。
"to which" 引导逗号后的补充性定语从句，"which" 指代前面的 "question" 或该问题所涉及的内容，并作介词 "to" 的宾语；该从句补充说明"对这个问题,我的回答总是……"，删去后前面主句仍可独立成立。
M: While most financial planners do give numbers, I don't think that's useful, as people are living in different areas with different costs of living, and have different needs and wants, which is why I suggest that people aim for financial independence.
M：虽然大多数理财规划师确实会给出具体数字，但我认为那没什么用，因为人们生活在不同的地区，有着不同的生活成本，而且需求和欲望也各不相同，这就是为什么我建议人们以财务独立为目标。
由which引导的非限制性定语从句,which指代前面"people are living in different areas...and have different needs and wants"这一整体情况,在从句中作主语。从句采用"which is why..."结构,其中"why I suggest..."是表语从句,说明原因的具体内容。
Another highlight was an hour-long walk to Kaitoke hot pools in the centre of the island, through wetlands and a forest, where we whiled away a good hour sitting in the pools shaded from the heat by layers of delicate umbrella-like plants.
另一个亮点是徒步一小时前往岛中央的凯托克温泉。途中我们穿过湿地和森林，在温泉池中消磨了整整一个小时；池子上方层层叠叠的伞状植物为我们遮挡了酷热。
“where”引导非限制性定语从句，修饰前面的地点名词“a forest”，并在从句中作地点状语。逗号表明该从句是补充说明，不用于限定“a forest”。从句主干为“we whiled away a good hour”，后接现在分词短语“sitting...”及其内部的后置修饰语。
Highly processed food tends to be softer, which makes it easier to chew and swallow.
高度加工的食物通常质地更柔软，因此更容易咀嚼和吞咽。
逗号将该从句与主句隔开，"which" 在从句中作主语，指代前面 "Highly processed food tends to be softer" 这一事实；从句说明这种柔软性使食物更容易咀嚼和吞咽，因此属于非限制性定语从句。
One type of disgust is called physical disgust, which protects us from eating or touching things that could be dangerous for us, such as raw meat or insects.
厌恶的一种类型称为生理性厌恶，它能保护我们免于食用或接触可能对我们有害的东西，例如生肉或昆虫。
逗号后的 "which protects..." 对前面的 "physical disgust" 作补充说明。"which" 在从句中作主语，且该从句用逗号隔开，删去后主句 "One type of disgust is called physical disgust" 仍然完整，因此是非限制性定语从句。
We also loved visiting the potter(陶艺家) Sarah Harrison, who showed us round her studio at Shoal Bay harbour, and her many pots and jugs, plates and bowls and colourful mosaics(马赛克).
我们也很喜欢拜访陶艺家莎拉·哈里森。她带我们参观了位于肖尔湾港口的工作室，还向我们展示了她制作的许多陶罐、壶、盘子、碗和色彩缤纷的马赛克作品。
“who...”由关系代词“who”引导，前后用逗号与主句隔开，补充说明前面的“Sarah Harrison”。“who”在从句中作主语，后面“showed...”的宾语包括参观她的工作室以及她制作的多种陶器，因此属于非限制性定语从句。
Many start off as part of larger plastic objects, which over time fragment into smaller and smaller pieces until they become tiny: 5 millimeters or less in diameter.
许多微塑料最初是较大塑料制品的一部分，随着时间的推移，它们逐渐碎裂成越来越小的碎片，最终变得十分微小，直径仅为5毫米或更小。
该从句由逗号后的关系代词 "which" 引导，对先行词 "larger plastic objects" 作补充说明；"which" 在从句中作 "fragment" 的主语。删除该从句后，主句 "Many start off as part of larger plastic objects" 仍然成立，因此属于非限制性定语从句。
"If we have had a great phone interview and then we wrap up and they don't have any questions for me, it pretty much ruins the whole interview. It tells me that the candidate is uninterested in the role, which in reality might not be the case at all," she notes.
她指出：“如果我们进行了一次很棒的电话面试，随后准备结束时，对方却没有任何问题要问我，那基本上就会毁掉整场面试。这会让我觉得候选人对这个职位不感兴趣，但实际上可能完全不是这么回事。”
逗号后的 "which" 引出非限制性定语从句，补充评论前面的整个判断 "the candidate is uninterested in the role"，而不是只修饰紧邻的名词 "role"。"which" 在从句中充当主语，"might not be" 是谓语部分。
Several lifestyle studies are getting underway soon, including one backed by the Alzheimer's Association called the US POINTER study, which will offer at-risk adults, ages 60-79, a series of lifestyle interventions(干预) to see if they impact Alzheimer's risk.
几项生活方式研究即将启动，其中包括一项由阿尔茨海默病协会支持、名为 US POINTER 的研究。该研究将为年龄在 60 至 79 岁、存在患病风险的成年人提供一系列生活方式干预措施，以观察这些措施是否会影响他们患阿尔茨海默病的风险。
该从句由逗号后的关系词 "which" 引导，补充说明前面的 "the US POINTER study"；"which" 在从句中作主语，"will offer" 是谓语，因此属于非限制性定语从句。
Though the study mentioned above was fairly small (only 191 women took the initial fitness test, which means it's hard to maintain statistical significance while breaking the group down into sub-categories of more or less fit), it does give us hope that dementia can be prevented or delayed through exercise in one's middle age.
尽管上述研究的规模相当有限（最初只有191名女性接受了体能测试，这意味着如果再按体能水平将参与者细分为更健康和不太健康的亚组，就很难保持统计学显著性），但它确实让我们看到希望：人在中年时期通过锻炼，或许能够预防或延缓痴呆症的发生。
逗号后的"which"引导非限制性定语从句，"which"在从句中作"means"的主语，并指代前面的整个分句"only 191 women took the initial fitness test"。
A big reason is that they are driven by unconscious urges, the biggest of which is emotion.
一个重要原因是，他们受无意识冲动的驱使，而其中最强烈的冲动就是情感。
该从句由逗号与前面的"unconscious urges"隔开，属于非限制性定语从句。"which"位于介词"of"之后，指代"unconscious urges"；"the biggest"表示这些 urges 中最大或最重要的一项，而该项是"emotion"。
But she does eat yogurt every day, which she said has "an infinite number of positive properties" for the body.
但她确实每天都吃酸奶，她说酸奶对身体有“无数积极的特性”。
"which" 指代前面的名词 "yogurt",从句用逗号与主句隔开,对酸奶作补充说明,因此是非限制性定语从句。"which" 在内部充当 "has" 的主语；"she said" 是插入语,交代信息来源,不影响从句的主谓关系。
A phantom jam begins when a car in dense traffic slows down even slightly, which causes the car behind that vehicle to slow even more—and the slowing action spreads backward through the lane of traffic like a wave, getting worse the farther it spreads.
幽灵堵车始于密集车流中的一辆车即使轻微减速，这会导致该车辆后方的车减速更多——并且这种减速行为像波浪一样在车道中向后传播，传播得越远情况越糟。
"which" 前有逗号,引导非限制性定语从句,补充说明前面整个事件(车辆减速)造成的结果。"which" 在从句中作主语,谓语是 "causes"。
There's also a qualified self, which is who I am, what are my activities, my social network, and all of these aspects are not reflected in any of these measurements.
也存在一个有条件的自我，即我是谁、我的活动是什么、我的社交网络以及所有这些方面都没有在这些测量中的任何一个中得到反映。
非限制性定语从句,用逗号与先行词"a qualified self"隔开。"which"在从句中作主语,后接系动词"is"和四个并列的表语成分(三个表语从句和一个名词短语),以及并列的谓语结构"are not reflected in any of these measurements"。整个从句对"qualified self"进行详细解释,说明其包含的内容维度及其未被测量反映的事实。
People living in rural areas, however, lag behind in online use, which limits their access to government services, banking and job opportunities.
然而，居住在农村地区的人们在网络使用方面落后，这限制了他们获取政府服务、银行业务和就业机会的途径。
"which" 引导非限制性定语从句，前面有逗号隔开，不能改用 "that"。这里 "which" 在从句中作主语，谓语是 "limits"；它不是只指某个单独名词，而是指前面“农村地区的人在网络使用方面落后”这一整件事，并说明这种情况限制了他们获得政府服务、银行服务和就业机会的渠道。
Unless employees are fully compensated, this could become a variant of parasitic(寄生的) capitalism, whereby corporate profits increasingly rely on extracting value from the public—and now personal—realm, rather than on generating new value.
除非员工得到充分补偿，否则这可能会成为寄生资本主义的一种变体，其中企业利润越来越依赖于从公共——现在还有个人——领域提取价值，而不是通过创造新价值。
whereby引导非限制性定语从句，修饰先行词parasitic capitalism，补充说明这种资本主义的运作方式。whereby在从句中作方式状语(= by which)，从句主干为"corporate profits rely on extracting…rather than on generating…"，含并列对比结构。破折号"and now personal"插入修饰realm。
When she did sleep, she experienced "problem-solving dreams," which left her feeling unrested when she woke up.
当她真的入睡时，她会经历“解决问题的梦”，这让她醒来时感觉没有休息好。
"which left her feeling unrested when she woke up" 由关系代词 "which" 引导，前面有逗号，补充说明先行词 "problem-solving dreams" 的影响。"which" 在从句中作主语，谓语是 "left"，宾语是 "her"，宾补是 "feeling unrested"，因此属于非限制性定语从句。
He recalled a recent paper he submitted to a journal, which accepted it only to request extensive editing, and then reversed course and rejected it.
他回忆起自己最近向一家期刊提交的一篇论文，该期刊接受了这篇论文，却又要求进行大量编辑，然后改变决定，拒绝了这篇论文。
"which accepted it only to request extensive editing, and then reversed course and rejected it" 由逗号加关系词 "which" 引出,对前面的名词先行词 "journal" 作补充说明。"which" 在从句中作主语，谓语由并列动作 "accepted"、"reversed"、"rejected" 构成；该从句不限定是哪一本期刊，而是补充这本期刊后续的处理过程。
But if there's one thing that triggers widespread employee frustration, it's an IT transformation project gone wrong, where swollen expectations have been popped and a long list of promised efficiencies has been reversed.
但是如果有一件事会引发员工普遍的不满，那就是失败的信息技术转型项目，在这类项目中，过高的期望已被打破，一长串承诺的效率已被逆转。
非限制性定语从句,由逗号引出,"where" 引导并在从句中作地点状语,先行词是 "an IT transformation project gone wrong"。从句内部包含由 "and" 连接的两个并列被动结构,共同补充说明项目失败的具体表现。
That's the conclusion of a recently released study, which analysed 259 bottles from 11 brands sold in nine countries, revealing an average of 325 plastic particles per liter of water.
那是一项最近发布的研究的结论，该研究分析了来自在九个国家销售的11个品牌的259个瓶子，揭示了每升水中平均325个塑料颗粒。
"which" 指代前面的名词短语 "a recently released study"，并在从句中作主语，谓语为 "analysed"；该从句前有逗号，属于对该研究的补充说明，删去后主句 "That's the conclusion of a recently released study" 仍可成立，因此是非限制性定语从句。
In my line of work, you hear a lot about talent, which is an idea we've mostly invented to give ourselves an excuse to be lazy.
在我的工作领域，你会听到很多关于天赋的说法，这是一个我们主要为了给自己找一个懒惰的借口而发明出来的概念。
非限制性定语从句，用which指代前面的"talent"，与先行词用逗号隔开；which在从句中作主语，表语为"an idea"；表达作者对才能概念的批判性观点——认为它是人为发明的概念。从句内部嵌套零引导的限制性定语从句"we've mostly invented"修饰idea，以及不定式短语"to give ourselves an excuse to be lazy"作目的状语。
"One of the risk factors for premature deaths is the air we breathe, over which individuals have little control," he said.
"过早死亡的风险因素之一是我们呼吸的空气，对此个人几乎无法控制，"他说。
非限制性定语从句，由逗号隔开，修饰先行词 "the air we breathe"。关系代词 "which" 与介词 "over" 一起前置(介词+关系代词结构)，"which" 在从句中作介词 "over" 的宾语。从句主干是 "individuals have little control over it(=the air)"，改写为 "over which individuals have little control"。
The alternative, he suggested, was to face the prospect of becoming another Palo Alto, California, where outsize stress on teenage students is believed to have contributed to a number of suicides in the last six years.
他提出，另一种选择是面对成为另一个加利福尼亚州帕洛阿尔托市的可能性，在过去六年里，人们认为那里对青少年学生过大的压力导致了多起自杀事件。
关系副词 "where" 引导,修饰先行词 "Palo Alto, California",前有逗号隔开为非限制性。"where" 在从句中作地点状语(= in which),从句主干为 "stress is believed to have contributed to suicides"(压力被认为导致了自杀)。
No matter how the math works out, you persistently view restaurants with voluntary tipping systems as being a better value, which makes it extremely difficult for restaurants and bars to do away with the tipping system.
无论计算结果如何，你始终认为采用自愿小费制度的餐厅更划算，这使得餐馆和酒吧极难废除小费制度。
"which" 引导逗号后的非限制性定语从句，并在从句中作主语，谓语是 "makes"。这里 "which" 指代前面整句所说的“人们一直把自愿小费制餐厅看作更划算”这一情况，补充说明其结果。
Even if they could, SimpliSafe claims that its system is always evolving, and that it varies slightly from system to system, which means there wouldn't be a universal magic formula for cracking it.
即使他们能够做到，SimpliSafe声称其系统一直在进化，并且系统之间略有不同，这意味着不存在破解它的通用神奇公式。
非限制性定语从句,由 "which" 引导,前有逗号隔开。"which" 指代前面整个主句内容(系统持续演进且各不相同),在从句中作主语。从句内部包含宾语从句 "there wouldn't be a universal magic formula for cracking it"。
英语四级真题中的定语从句共标注出 2728 处实例，按子类型分为 2 类：限制性定语从句 2313 处、非限制性定语从句 415 处。本页从中精选 50 句真题例句，出自 19 套真题卷，句长 11–54 词（平均 28 词），CEFR 等级构成为 C1 36 句、B2 10 句、B1 3 句、C2 1 句。以主句为第 1 层计，这 2728 处实例最集中的位置是第 2 层（1696 处），最深嵌套到第 7 层。每句以高亮标出定语从句在原句中的位置，附中文翻译、逐句解析、出处试卷与卷面位置，并可进入单句详情页查看结构树逐层拆解。
关于英语四级真题中定语从句的出现频次、常见引导词与嵌套深度，最常被问到的问题。
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