问题描述：
by the time引导的时间状语从句和when引导的时间状语从句有区别吗
eg.:By the time I got outside the bus had already left.
When she got to school,she realized she had realized she had left her backpack at home.
eg.:By the time I got outside the bus had already left.
When she got to school,she realized she had realized she had left her backpack at home.
问题解答：
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