1. 有一组单项式：$a^2$，$-\frac{a^3}{2}$ ，$-\frac{a^4}{3}$ ，.........，请观察它们的构成规律，用你发现的规律写出第10个单项式：____ ．

多次重复实验均获得相同实验结果．请回答：

    Hello，I am Judy．In summer I like wearing a____．It is cool．In autumn I like wearing ____．I like hopping and jumping．In winter I like wearing a____．Because it is warm．What do you like，Jim? I like wearing sport____every day. Because I like running．How about you，Alice? I like____．This Sunday I will buy it．