Question

Having finished his homework ,the boy went to play computer games.中having能不能换成have或had

我知道用having 是因为非谓语动词，但用had看做过去完成时不一样吗

Answer 1

不能，要分词短语作状语

Answer 2

非谓语动词是这么来的

After he had finished his homework ,the boy went to play computer games.

the boy 和he ，主语是同一个人，所以从句的主语和介词可以省略，用非谓语动词的形式表示。

但你直接用had，从句就不完整了，必须把主语和介词加回去才符合游戏规则。