A    

    People's hobbies aren't always the same. They change with many things. Here are some examples:

Age

    Hobbies change with your age. When you're a kid, you may be interested in playing games, collecting toys etc. When you study at school, you may be interested in sports, pop music and movie stars. When you're old, you may be interested in chatting and listening to Beijing Opera.

Job

    Hobbies change with people's jobs. Teachers may like staying with their students. Doctors may like all kinds of medicine. Drivers may like all kinds of vehicles and athletes may like all kinds of sports games.

Season

    Hobbies change with seasons. People may have different hobbies in different seasons. In spring, you may like flying kites. In summer, swimming is a good choice(选择). In autumn, you may like to go hiking and in winter, skating must be great fun.

长方形的一条长加一条宽等于周长的____；正方形的周长是边长的____倍

He____(相信)you were right，but I didn't

形如 $a{x}^n+b=0$（ab≠0）的方程叫做二项方程.下列方程中是二项方程的是（     ）

关于元电荷、点电荷的说法，下列说法正确的是（  ）