Last night,not until ____ my homework ____

问题描述:

Last night,not until ____ my homework ____
a.did I finish; I went to bed
b.I had finished; did I go to bed
这里怎么选择B?应该是not until之后就是倒装呀,A怎么错了?

not until放句首时是要用倒装,但是是主句倒装,非从句倒装.
A选项就是倒装了从句没倒装主句.所以选B不选A