Question

Passengers must not leave their seats ________ the plane comes to a full stop.

A. until

B. since

C. if

D. because

Answer

A

【解析】句意：在飞机完全停止之前，乘客不得离开座位。A) until直到，在…以前，短语not…until…：直到…才…；B) since自从…以来，既然； C) if如果，是否；D) because因为。结合句意和语境可知选A。

点睛：until / not...until之间的区别： （一）until“直到”,表示某一种行为一直持续到某一时间。用在肯定句中，句子的谓语动词必须是可延续性的如live, study，wait , last, love, like, stay, work, continue 等。。 not...until“直到...才”表示直到某一时间,某一行为才发生,之前该行为并没有发生. 用在否定句中，主句中的谓语可以是延续性的也可以是短暂性动词。 例如，1. I studied English until 9 o'clock last night. 我咋晚学英语一直学到9点钟.(表示9点前一直在学) 2. I did not study English until 9 o'clock last night. 我咋晚直到9点钟才学英语.(表示9点才开始学) 3. I waited for five hours until it was dark. I had to give it up. 4. I didn't go to sleep until 11 o'clock （二）not until 还可以用于强调句中，有两种结构，结构A：It is (was) not until + 时间状语(从句)+ that +主句。例如，5. It was not until he came back that I went to sleep.

也可以放在句首，句子要采用部分倒装，其结构B：Not until +时间状语(从句)+主句的倒装句6. Not until he came back did I go to sleep.