【英语选择】I have no idea how many years ago ___the custom begain became more popular a...

问题描述:

【英语选择】I have no idea how many years ago ___the custom begain became more popular a...
【英语选择】I have no idea how many years ago ___the custom begain became more popular
a.it was when
b.it was that
c.was it that
d.was it when
怎么答案不一样。你们说说你们答案何以见得?

B
从句可以变成It is many years ago that the custom begain to became more popular
强调句型