犯错误是正常的可以说It is normal to do sth吗?还是用nature?

是it is time to do sth还是 it is the time to do sth 可以说it is suitable for sb to do sth 是sth is important to sb还是 it is important for sb to do sth? It is fun?到底是It is fun to do sth 还是It is fun doing sth?It is 可以说sb is suitable to do sth? It's time to do sth是固定用time to do sth,还是说名词加to 加do sth 有个这样的 it is good not to do sth 还是 it is good to not do sth? it is too +adj to do sth 还是it is too +adv to do sth 请问是I find it difficult to do sth还是I find it is difficult to it is difficult to do sth对还是it difficult to do sth对 it is hard to+Ving还是to do sth It is fun to do sth对,还是It is fun to doing sth