Bill 's hat was blown off when he was crossing the bridge .变成have+object+p.p.
问题描述：
Bill 's hat was blown off when he was crossing the bridge .变成have+object+p.p.
答
楼上的那个虽然语法没错 但是句意不符合 楼上的意思变成了BILL使他的帽子被吹下来了
应该是风 因此是The wind have got Bill's hat blown off when he was crossing the bridge .
希望能够帮到楼主