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1. The fronts of the notes show windows or gates while the backs show bridges. （Unit 10 Culture Corner） while在此表示对比，意为“而；然而”。 I do every single bit of housework while my husband Bob just does the dishes now and then. 我做家里的每一项家务，而我丈夫鲍勃只是有时洗洗盘子。 while还可引导时间状语从句，意为“当……的时候”，此时的主从句谓语动词通常是延续性动词。 The computer system broke down suddenly while he was search……