我昨天直到写完作业才回家.I didn't go home until ________________ yesterd

I finished my homework
until引导的是时间状语从句,状语通常由副词、介词短语、动词不定式、分词和从句等担当.例如：She didn't go to bed until her daughter came back.
在题目中,而until后面最好是一个句子,finished my homework不符合上面的要求且很明显缺少了主语成分,故不能选填.
until的一些用法:
until用在肯定句,谓语动词通常是延续性动词,如stand,stay,talk,wait等,表示主句动作终止的时间.如:
③I waited until he came back.我一直等到他回来.
④The war lasted until 1945.战争持续到1945年.
如果用在否定句,谓语动词通常是瞬间性动词,如open,start,leave,arrive,finish,stop等,强调主句动作开始的时间.如:
⑤I didn't leave the boy until his mother turned up.直到这孩子的母亲来,我才离开.
⑥The noise of the street didn't stop until it was midnight.街上的噪音直到半夜才停止.

i finished my homework ;until 后+从句，是个完整的句子。请看下面的解释与例句。
当主句是否定句时，它引出的意思是"直到（某时）（某动作）才（发生）" ，这时候常会出现"not until …"的结构，如果将 "not until …"的结构放在句首，那么主句要写成倒装句。例如：
He didn't go to sleep until 12 last n...

I finished my homework
后面要加一个从句，要有主语I

I finished my homework

I finished my homework
因为 until 是连词,连词后面跟一个完整的句子.