加与不加均可find it+形容词 to do sth= find (that) it's +形容词 to do sth.前者为单句,后者为复句,中学里经常进行单复转换的.如I find it hard to keep the room clean=I find that it's hard to keep the room c...不加that呢？比如i find it is useful.这样对吗对的，宾语从句中，引导词that常省略