情態動詞也可以和動詞進行形式或完成進行形式構成謂語：表示“應當正在……”，“想必正在……”的意思。
【例如】
Why should we be sitting here doing nothing?
She might still be thinking about the question you raised.
He can’t be swimming in such weather.
At the moment she may (might) be playing with her schoolmates.
We needn’t be standing h......