用所给词的适当形式填空。（10分。）
1.My brother is ______ (thin) than his classmate.
2.What would you like?  I’d like ________( buy) two kilos of peaches.
3.The       (two) lesson is much easier than the fourth one.
4.Ben and Benny are good at         (skate).
5.The boys            _ (run) in the playground now.