whenness时间性
whenadv.什么时候;当 ... 时conj.然后;可是;当 ... 时pron.什么时候n.时间
When speed becomes a problem.当节奏成为问题时。
When was the Bible written?
When your world's crashing down
When does the curtain fall?
When you return to Germany?
When did the symptom begin?
When will the dinner start?
When does this store close?
When did this custom start?
When is the assignment due?