not until this term__to realize how important this subject is to _英语解答

not until this term__to realize how important this subject is to his future career as a diplomat
A.he began
B.did he begin
C.has he begun
D.thath he has begun
选什么?为什么?
答案是B为什么？

人气：261 ℃　时间：2020-07-10 00:48:23

解答

b
not...until 表示直到.才.
当把not until 置于句首时,要倒装
He didn't realize how important the subject is to his future career as a diplomat.
原来的时态应该是过去时,表示以前的一个动作或状态,不该用完成式,
此处的this subject is 可认为是常识,真理.没必要用过去式.