what fun it is to swim 为什么不能用how?

what fun it is to swim 为什么不能用how? What fun it is to play .这里的what为什么不能用how? ____great fun it is to swim in summer!A how B what C what a what a fun it is to swim in summer. 为什么是what fun it is to.而不是how funn it is to. 为什么能说What fun it is to do sth.却不能说How fun it is to do sth. what fun it is to listen music 这里的fun为什么不能是形容词用how fun. 为什么是what fun it is to. how fun it is to do … what fun it is to do… 为什么要用后者,fun如果当形容 （）fun it is to have ice cream in hot summer!填what还是how 为什么? 为什么说what fun it is!而不用how fun it is?这是什么句型? what fun it is和how fun it is