The book was written in 2001,___the education system has witnesse_英语解答

The book was written in 2001,___the education system has witnessed great changes.
A.in which B.since when 为什么不选A?

人气：268 ℃　时间：2020-05-23 14:07:51

解答

根据后面的HAS WITNESSED （现在完成时）可知是用SINCCE WHEN,如果用A是一般过去时.
加油!不明白再问!