_____(How/What) fun it is to talk with some friends online!

_____(How/What) fun it is to talk with some friends online!
_____(How/What) fun it is to talk with some friends online!

_____(How/What) fun it is to talk with some friends online!
How fun it is……
根据搭配 what+(a/an)+adj.+n.+主语+谓语+(it is)； How+adj.（adv.）+主语+谓语+(it is)
这里fun 是做形容词的,并且后面没有修饰的名词,所以用how

How

___What__(How/What) fun it is to talk with some friends online!
出现it is关键词，必须用what。固定用法 。楼上都是错的

How

what
这儿的fun 是不可数名词

how
表惊叹