Not until I completed the form did I realize that half the q

not ... until... 结构中, 主句和从句都是用的一般过去时.

如: I didn't go to bed until I finished my homework .

变成倒装句后,就成了: Not until I finished my homework did I go to bed .

你这个问题中的句子也是一样, 其主句本身就是一般过去时.

I didn't realize that half the questions were not relevant to me until I completed the form .

因此变成倒装句后,只能用did I realize而不能用had I realized.

你把这句话的原句还原，就是I didn't realize that half the questions were not relevant to me until I completed the form .强调句要把not until提前，用倒装句所以是did i realize

你好，同学，这是一个倒装句，原句是

I didn't realize that half the questions were not relevant to me until I completed the form.

翻译：直到我完成了表格，我才知道一半的问题与我无关。

还原这个句子，可以看出completed 在前，而realize...

complete这个动作在realize之前，故不用完成l