题目

The children vary considerably in the rate at which they learn these lessons. _____, we make the teaching plans different accordingly. A．Because of this reason                            B．It is because C．As a result of                                         D．For this reason 答案：D在平面直角坐标系内，点A的横坐标、纵坐标合起来叫点A的________，它是一对________．