英语动词在句首时,什么情况下不用变成动名词

英语动词在句首时,什么情况下不用变成动名词

doing ,done ,do ,to do ,四种
doing 用于独立主格结构,表示主动和进行时
For example:
Walking in the street,a stone fell down.
Hearing the news,she laughed..
done 也用于独立主格结构,表示被动和过去时
For example:
Punished,the boy cried.
to do 表目的
For example;
To catch the early bus,he got up early.
以上三种都用于从句
do 用于祈使句,即省略主语 ,可直接作动宾式句子
Open the door ,please.