The river is so deep that the children can't swim in it.——
问题描述：
The river is so deep that the children can't swim in it.——
The river is too deep for the children to swim in .(从句中的it要去掉),这里的“从句中的it要去掉”怎么解释,原来的句子不是从句吗?
答
The river is so deep that the children can't swim in it.——是原因状语从句,所以从句中要加it,构成the children can't swim in it的完整句子.
The river is too deep forthe children to swim in.---- 是简单句,所以不加it,再如：
I need a chair to sit on.
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