Ⅰ.用所给词的适当形式填空
1．Which is ____________ (small)，the sun，the moon or the earth?
2．The air in Beijing is getting much ________ (clean) now than a few years ago.
3．Mobile phones are very popular now and they are ________ (cheap) than before.
4．This room is twice ____________ (big) as that one.
5．This necklace looks ______ (nice) and sells ______ (well)．
