题目内容：

Mary was heard ___ just now.A laugh B to laugh 为什么选B?不是感官动词后面省略to吗?

优质解答

这种变为被动句后加上to的情况一般出现在make等词身上……像是She was made to work all day.
用作感官动词时,如果是do sth要加to,如果是doing sth就不加.
但是这种事只出现在被动句中^_^