be动词后加动词什么形式

回答如下
进行时+doing
被动式+过去分词

参考

动词ing

be动词后面的动词形式有三种可能：

①-ing:现在进行时,I'm trying to give you the right answer.

②-ed:被动语态,I'm told that you don't know her.

③-to do:

1、表示按计划或安排要做的事.例如：They said goodbye,little knowing that they were never to meet again.他们告了别,不知道以后再也不会见面了。

2.表示“应该”,相当于should,ought to.例如：You are to report to the police.你应该报警。

3.表示“必须”,相当于must,have to.例如：The letter is to be handed to him in person.这封信必须亲手交给他。

4.表示“想,打算”,相当于intend,want.例如：If we are to be there before ten,we’ll have to go now.如果我们要在十点前到,我们现在就得走。