Question

【题目】Frank fell asleep ______ he was having an English class.

A. while B. before C. as soon as D. until

Answer 1

【答案】A

【解析】句意：当Frank正在上英语课的时候他睡着了。while当…时候，引导时间状语从句；before在…之前；as soon as一…就…；until直到…时候。根据句意和从句中使用的时态可知应选A。while引导时间状语从句时，从句中谓语动词应该是持续性的，常用进行时态，主句用一般过去时态。