关于不定式作名词的修饰语：There's work to be done.
There's work to be done.
和
I gave Bill an apple to eat.
两句话的不定式分别修饰“work”和“apple”,都是被do和被eat,
为什么一个用被动be done 一个用主动 eat.
There's work to do.
和
I gave Bill an apple to be eaten.