It's often said,a friend is to man_____water is to fish.横线处一定要填what?不能填 as?

问题描述:

It's often said,a friend is to man_____water is to fish.横线处一定要填what?不能填 as?
那填what的话要怎么理解呢?可不可以改为“To man,a friend is what water is to fish”?
求详解·····

这是个固定句型,我记得是高中时候学的.A is to B what C is to D.
翻译成A对于B就像C对于D一样.这句话的意思是朋友对人类来说就像是水对鱼般重要.
你这种改法倒是没见过.好吧,搞了半天是固定句型·····是滴。