题目内容：

英语词汇题目
Who is the first__(know) this news?
A bird was seen __(fly)into the room

优质解答

knowing 用到了一个结构be first doing sth
to fly 鸟被看见飞进屋里 fly是瞬间动词 不能“被看见 正在飞进屋里” 所以不能是see doing 是瞬间动词时,只能是see do 改被动语态就必须be seen to do