定语从句的两问题,高手进。

Question

1.定语从句The book was written in1946,___the education system has witnessed great changes.
A.when B.during when C.since then D.since when
这是一高考题，答案是D，据说是相当与since which time
然而我又遇到这样一道题，如
In the office I never seem to have time until after 5:30 p.m., ____ many people have got home.
A. whose time B. that C. on which D. by which
如果就选答案的话，只有选D，答案也是D。但是这就与上题不就冲突了吗，应该是by which time或是by when???

Answer 1

第一句分析正确。
第二句by which就是by which time，因为主句有一个time，为避免重复就不说time了。

when一般用作疑问副词；但有时也可用作疑问代词，作since, until, up to 等少量几个介词的宾语，如until when, since when, up to when。
按道理来讲，第二题的by which time就是等于by when。但语言不仅要讲道理，更要讲习惯。再合乎逻辑的说法，如果大家口头上都不这样说，那也只能认为它是错的。by when这种说法目前我还没见过。

Answer 2

两个句子都是定语从句来分别修饰year和time
第一个句子的when指代1946年，在从句中作介词since的宾语，充当从句的时间状语成分
第二个句子的which指代5:30pm，在从句中作介词by的宾语，也是做从句的时间状语成分
因为两个从句都是完成时态，所以时间状语分别由since和by引导，跟when和which不冲突

Answer 3

In the office I never seem to have time until after 5:30 p.m., ____ many people have got home.
A. whose time B. that C. on which D. by which
此句子前面已经出现中心词time，后面避免麻烦就省略了，其实就是by which time或是by when