为什么说what fun it is!而不用how fun it is?这是什么句型?

为什么说what fun it is!而不用how fun it is?这是什么句型? what fun day it is?为什么用fun,不用funny 不是说what+n.+主谓吗,但为什么说是what fun it is to do sth呢? _____ fun it is!A.What B.How不是可以说 It is fun!为什么不能说 How fun!____ fun it is to visit Beijing Hutong on foot!知道fun可以做名词,但是不是也可以说It is fun to visit .真把我搞糊涂了!好几天过去了,难道没有 what fun it is to listen music 这里的fun为什么不能是形容词用how fun. what great fun it is to go hiking!为什么因为fun是不可数名词不加a,而不说它抽象名词具体化呢?还是因为fun不属于抽象名词具体化的范畴? what fun it is to swim 为什么不能用how?fun为形容词为什么不行，陈述句形式It is fun ti swim, what great fun it is to go hiking in such fine weather!和what a great fun .!哪个对?为什么? What a ____(fun)story it is! what fun it is to=how____ 为什么是what fun it is to. 如题What fun it is中fun是什么 what fun it is to jump into a river on a hot day.为什么用what fun instead of how fun 英语it is to jump into a river in summer!A how fun B how funny C what great fun D what a great fun为什么 what fun it is! 这个fun前面是不是要加a或者what改fun? what great fun it is to go camping in such fine weather,为什么不说what a great fun it is to gocamping in such a fine weather? 为什么是what great fun it is!而不是what a great fun it is! what a fun it is to swim in summer.为什么要去掉a呢?不是how fun啊