when he _____something useful,he wasted his time drawing little pictures.a.must have done b.shall be doing c.should be doing d.should have been doing

when he ____ young When he was a When was he at What does he do when he works he played when he was at when he can come还是when can he come When was he born,为什么不是When was he bear? when he came near还是when he came nearly when he leave 和when he is leaving区别 when he came back to when was he born=--- ---- he first started a___ when When he will come back When does he get up? when does he have history? When did he graduate( )college when was he ten 急用 well when he finishde reading