今天我们来分析这个句子。原句The relevant behavior here is the speed and care with which drivers operate their cars.我们先做句式成分拆解，整句为主系表基本句型，主语是The relevant behavior here，here作后置定语修饰主语the relevant behavior，谓语系动词为is，表语是并列名词短语the speed and care，后半部分with which drivers operate their cars是介词+关系代词引导的限制性定语从句，这也是本句核心语法考点，很多学习者容易把这类从句和普通who/which/that定语从句混淆，也分不清介词该如何搭配、关系代词该用哪一个，首先明确核心定性：本句属于“介词 + 关系代词”引导的限制性定语从句，先行词是the speed and care两个并列抽象名词，关系代词选用which，搭配固定介词with，还原从句语序就是drivers operate their cars with the speed and care，直译就是“司机以这样的速度和谨慎程度驾驶车辆”，整合整句翻译：这里所说的相关行为，指的是司机驾驶车辆时的速度快慢与谨慎程度。
接下来逐个拆解核心语法知识点，第一，什么是介词+关系代词定语从句：在定语从句中，当关系代词which/whom在从句中充当介词宾语时，可以把介词提前放置在关系代词之前，形成“介词+which/whom”结构，that和who不能用于这种介词前置结构，这是高频易错点，同时这类从句只可用which指代事物、whom指代人，绝对不能用that替换，也不能把介词随意放在从句末尾而忽略搭配逻辑；第二，介词的选择依据，主要有三个原则，一是和从句中的动词形成固定搭配，本句中operate本身可搭配with，表示“以某种方式、某种状态行事”cinema，with the speed and care是固定语义搭配，表“凭借速度与谨慎态度”；二是和先行词形成固定搭配，根据先行词的固定介词搭配来确定前置介词；三是根据句子语境语义逻辑，按照要表达的含义选择合适介词，如in、on、at、for、with、about等。
第三，先行词为并列名词时的用法，本句先行词是the speed and care两个不可数抽象名词并列，依然统一用which指代，不需要拆分关系代词，从句谓语动词根据语义保持原形即可，无需受并列名词单复数干扰；第四，句式还原技巧，遇到看不懂的介词+which从句，直接把关系代词还原成先行词，把介词放回从句末尾，就能变回普通定语从句语序，本句还原后就是The relevant behavior here is the speed and care (which) drivers operate their cars with，和普通定语从句结构完全一致，只是为了句式正式、表达高级，将介词提前到which前面，这种结构在书面英语、考研阅读、四六级长难句、外刊写作中出现频率极高，口语中反而更习惯把介词放在句尾。
接下来列举同语法知识点的经典例句，覆盖不同介词、不同先行词、人和事物两种情况，方便举一反三：例1，This is the room in which we held the meeting yesterday一流范文网，还原：we held the meeting in the room，解析：介词in和先行词room搭配，表“在房间里”，in which可等同于where；例2，The person to whom you spoke just now is my English teacher，还原：you spoke to the person，解析：先行词指人，用whom，介词to和动词speak固定搭配；例3，I still remember the reason for which he refused the invitation，还原：he refused the invitation for the reason，解析：介词for和先行词reason固定搭配，for which等同于why；例4，There are many ways in which we can solve this difficult problem，还原：we can solve this difficult problem in many ways，解析：in ways为固定搭配，表“以多种方式”。
例5，The book about which we talked last week is very popular among students，还原：we talked about the bookcinema，解析：介词about和从句动词talk固定搭配；例6，The prize for which he worked so hard finally came to him，还原：he worked hard for the prize，解析：介词for表“为了某物”，语义逻辑确定介词；例7，The old house in which my grandfather lived has a long history，还原：my grandfather lived in the old house，in which指代地点。
例8，The topic with which they are discussing now is about environmental protection，还原：they are discussing the topic with... 此处with贴合讨论的伴随状态，遵循语义搭配原则；例9，The girl with whom he went to the cinema is his deskmate，先行词指人，whom作介词宾语，不可用who/that替换；例10，The time at which the train arrives is fixed every day，还原：the train arrives at the time，介词at和先行词time固定搭配。
再梳理常见易错陷阱，第一，很多学习者会写成with that、in who，这是绝对语法错误，记住口诀：介词后只接which/whom，绝不接that/who；第二，随意乱用介词，不考虑固定搭配，比如本句不能换成in which、for which，必须遵循operate with和先行词的语义搭配；第三，分不清限制性和非限制性定语从句，介词+which同样可以引导非限制性定语从句，前面加逗号，如He bought a new car, with which he traveled all over the country；第四，看到并列先行词就用what、that混淆关系代词，牢记事物统一用which，人统一用whom。
最后做完整知识点总结，介词+关系代词（which/whom）引导定语从句是高中至大学英语、各类考试长难句核心语法，也是书面写作提升句式高级感的关键用法，核心规则可归纳为三点，其一，关系代词限定：指物只用which，指人只用whom，介词后禁用that、who；其二，介词三大选择逻辑：从句动词固定搭配、先行词固定搭配、语境语义逻辑，无需死记硬背，学会句式还原就能快速判断；其三，句式用法区别：正式书面语多用介词前置结构，口语习惯把介词留在从句末尾，语法上都成立，但写作、阅读中优先掌握前置结构；其四，遇到并列先行词、时间地点原因类先行词时，依然遵循统一指代、固定介词搭配原则，同时要区分in which和where、for which和why、at which和when的互换关系，掌握这一语法点不仅能快速拆解长难句，读懂外刊、阅读理解中的复杂句式，还能在英语写作中替换简单普通定语从句，让表达更地道专业，原句正是典型的书面正式表达，用with which衔接先行词和从句，凝练流畅，避免了口语化的零散句式，也是英语抽象名词作先行词时最常用的语法结构，吃透这一个句式就能辐射同类上百种长难句的拆解与运用。
