1.These young trees must _be well looked after_____
如果要选第一个,必须是这样的形式:These young trees must __be taken good care of.
2.I like the car but it _costs____too much.
因为主语是车,所以花费要事务;spend的主语是人.
3."Leave" it with me and I'll see what I can do.
把它留给我,我看看能做点什麽.
这里的leave不是主语,这是个祈使句,所以动词用原型.