選c.這是個(gè)強(qiáng)調(diào)句型.it was...that
在這里強(qiáng)調(diào)的是until引導(dǎo)的時(shí)間狀語短語.還原一下是這樣：
He didn't go back home until midnight after the long-lasting conference.
在強(qiáng)調(diào)until引導(dǎo)的短語或者從句時(shí)要注意把not提到until 前面一起放到被強(qiáng)調(diào)部分,也就是it is和that中間.
He didn't go to bed until he finished his homework.
變?yōu)閺?qiáng)調(diào)句型：It was not until he finished his homework that he went to bed.
注意,把not提前后,went 用肯定形式了,也就是主句的謂語動(dòng)詞用肯定形式了.
祝學(xué)習(xí)愉快啊!