This exercise is so difficult that few of us can do it.为什么后面的it 不能省略?

This exercise is so difficult that few of us can do it.为什么后面的it 不能省略? This Is Not An Exercise 歌词 this is good exercise 为什么不是this is a good exercise ? this is so sad this is so sad This is so solit Li Ming often does exercise,so he is very a ( ) This exercise is difficult A so ,that few of us can do Btoo,for any one of us to do it 这两个答案为什么错 This is _____easy exercise填an还是a This exercise is easy to do.(改为复数形式) This world is so cold ,so sad.. this winter is so cold This is so un-me! This exercise is ___ different ____.A so;that few of us can do B so;that few of us can do itC very;for anyone of us to doD very;for anyone of us to do it 连词成句：some you do faffer exercise this you are should year so ( )-Tomorrow is a holiday.Why are you doing your homework?-I'm doing this exercise now so that I won't have___on sunday.A.for B.them C.it D.to但是不明白为什么,后面为什么不接宾语? 题目是用所给词的适当形式填空 This exercise is not ——（hard） I can not jump so——（high）I am sure the soup tastes ——（good） This exercise is ____ difficult ____.A.so ; that few of us can do itB.too ; for anyone of us to do为什么答案是A?B 错在哪儿?