题目

which后面加逗号是不是就意味着修饰前面的整个句子或主语,不加逗号就是修饰前面跟着的名词?
就是好像很多句子当中的有的which前加了逗号,但是好像也没有修饰前面句子中的主语或整个句子?
这些句子是在SAT的OG上出现的,
P534 As children mature,they develop an independence that their parents,who have been responsible for them since they were born,often find difficult to accept.(这个句子里面的who前也加了逗号,但为什么是修饰parents 而不是children
P534 Ms.Kovak proundly dsplayed her research group's most ingenious invention,a vacuum cleaner that emptied its own dusy bag when people press a botton.(这个when 跟在bag 为什么有会修饰句子主语呢?

提问时间：2020-11-28

答案

很多情况下是间隔定语从句,比如第一个,根据意思很明显who从句是修饰parents的,完整的定语从句是their parents often find difficult to accept.做independence的定语,而 who have been responsible for them since they were born,是parents的定语,不加逗号当然可以,但是不加逗号你觉得一长句话你能分清在哪里断开不?加了逗号,句子层次很明显的.
第二个不是定语从句,是状语从句,意思是他人们按下那个键时真空清洁器就清空灰尘了.做的是时间状语.
有什么疑问还可以问我,我一直在线.