Question

The book was written in 1946, ________ the edu--cation system has witnessed great changes.

1. A.
   when
2. B.
   during which
3. C.
   since then
4. D.
   since when

Answer 1

D
句意：这本书写于1946年，从那时起教育体制开始发生巨大变化。因为从句中时态为现在完成时，故选since when来引导这一定语从句。A、B两项引导的从句应使用过去某种时态；C项只是充当后面从句中的时间状语，而不能充当引导词，来引导该从句，故排除。