因为fools 是fool加s,为名词,愚蠢的人,而不是做形容词“愚蠢”的意思
对于感叹句：what修饰名词或名词短语,有以下两种形式
1.What+a(an)+（形容词）+单数可数名词+主语+谓语!或是：What+名词词组+主语+谓语!如：
What an apple this is!What a fine day it is!
2.What+(形容词）+可数名词复数或不可数名词+主语+谓语!
What kind women they are!What nice music it is!
由How引导的感叹句.
how用来修饰形容词、副词或动词.其结构是：How+形容词（副词）+主语+谓语!
How hard the workers are working!
How clever the girl is!
How quickly the boy is writing!
注意：当how修饰动词时,动词不跟着感叹词提到主语之前.
How the runner runs!
what与how引导的感叹句,一般情况下可以相互转换,转换后意义不变.如：
What an interesting story it is!==How interesting the story is!
what a beautiful building it is!==How beautiful the building is!
你上面的句子如果要用how,可改为：How fool you are!
