Question

After a 5-year absence, we returned to our mother school, and not until then       it was such a beautiful school.

A．we realized

B．had we realized

C．we had realized

D．did we realize

Answer 1

D

考查部分倒装。not until放在句首时，后面句子要部分倒装，排除A,C；根据then，可知要用一般过去时态，所以选D。