郁闷的题1。 Easy as we made it___the importance to keep earth in

郁闷的题
1。 Easy as we made it___the importance to keep earth in place,some villagers would't listen.
A.to understand B.understood C.understanding D.to be understood

2.It is not where someone comes from and what a person looks like__is important but ___he grows up to be.
A.that:that B.what:what C.,it D.that :what
3.--Who do you think is the best in our class?
--Qell,I'm afraid there's no__answer.
A.easy B.quick C.fixed D.certain

第一题和第二题应该选 什么呢？请对错误答案予以解释。
第三题答案是B，为什么不选C和D呢？