我知道你一定是what的用法的疑问what引导的是一个类比性状语从句,说明主句行为的方式、方法,其结构为“A is to B what C is to D”,意思是“A对于B来说,就像C对于D一样”。 Intellect is to the mind what sight is to the body.
还可以这样说:The cultural diversity to human civilization is just like air to the earth.