It is fun to do sth.句型fun的词性

It is fun to do sth.句型fun的词性 It's fun to do sth.中的fun什么词性 lt is fun to do sth.的fun 的词性是什么? It is fun to do sth造句 It is fun to do sth.造句. It is fun?到底是It is fun to do sth 还是It is fun doing sth?It is It is fun to do sth对,还是It is fun to doing sth what great fun it is+to do sth 吗 it is a great fun to do sth. 为什么能说What fun it is to do sth.却不能说How fun it is to do sth. it is +形容词+to do sth ,为什么有些资料上是it's fun +to do sth,fun是形容词吗 it is fun to do 还是 doing?