问题
选择题
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
答案
答案：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。