Question

把非谓语动词改写成复合句？

Seeing the teacher entering the room，the students stood up.（现在分词作状语）改写成完整的复合句？

是： When the students saw the teacher entering the room, the students stood up.
还是：When the students were seeing the teacher entering the room，the students stood up.
我也不确定到底是哪个，还请高手过来权威鉴定一下~
Heated，the metal expands.（过去分词作状语）改写成完整的复合句？
是： When the metal is heated, it expands.
还是：While the metal is heated, it expands.
还是：If the metal is heated, it expands.
我也不确定到底是哪个，还请高手过来权威鉴定一下~

Answer 1

When the students saw the teacher entering the room, the students stood up.

When the metal is heated, it expands.

追问

为什么是你写的这样呢？

追答

were seeing 是过去进行时 原来句子中seeing 只是做状语 因为与后面句子的主语 学生是主动关系所以用的是seeing 与时态无关

个人觉得后面的语法上应该都没问题 这句是不是应该是If the metal is heated, it will expand.

时间久了 很多东西都不确定 有些时候语感很重要

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感谢