it作形式宾语,wise作宾语补足语.to interfere作真正的宾语.I think it difficult to give up smoking.it作形式宾语,difficult作宾语补足语.to give up smoking作真正的宾语.I think（that) it is difficult to give ...那是不是consider itis difficult to give up smoking这句话是错的 因为这里that不能省？consider itis difficult to give up smoking这句话对的，that 可以省略的，因为这里that引导的是宾语从句，在这里可以省略