题目

The road is always busy. Look out when you walk_______.     A. beside            B. along              C. below            D. across 答案：D在以点电荷为球心、r为半径的球面上各点相同的物理量是 (   )A．电场强度         B．同一电荷所受的电场C．电势             D．同一电荷具有的电势能