比較while, when, as

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19.8 比較while, when, as
	1）as, when 引導短暫性動作的動詞。 　　　 Just as / Just when / When I stopped my car, a man came up to me. 2）當從句的動作發生於主句動作之前，只能用when 引導這個從句，不可用as 或 while。 　　　 When you have finished your work, you may have a rest. 3）從句表示"隨時間推移"連詞能用as，不用when 或while。 　　　 As the day went on, the weather got worse.　 　　　日子一天天過去，天氣越變越壞。