下列描述中,属于我国北方地区地理环境特征的是( )
A:河湖众多,水网纵横
B:气候湿润,降水充沛
C:平原高原为主,地形平坦
D:深居内陆,气候干旱
—I think my Maths teacher is working hard. He teaches us very .
—Yes, but he can't come today. He doesn't feel .