( )The book was written in1946,_____ the education system has witnessed great challenges.( )The book was written in1946,_____ the education system has witnessed great challenges. A.when B,during which C.since which D.since when 答

Question

( )The book was written in1946,_____ the education system has witnessed great challenges.
( )The book was written in1946,_____ the education system has witnessed great challenges.
A.when B,during which C.since which D.since when

答案选D,B和C哪里错了?为什么要用when来代先行词1946,而不用which?
求大神详解

Answer 1

( )The book was written in1946,_____ the education system has witnessed great challenges.
A.when B,during which C.since which D.since when
选D
根据has witnessed great challenges现在完成时,可知要用since引导时间状语从句.因为the education system has witnessed great challenges句子的主谓宾成分完整,which是关系代词,定语从句不需要做主语或宾语的which.定语从句缺少表时间的关系副词when.