题目

在正电荷Q的电场中的P点放一点电荷，其电荷量为+q，P点距离Q为r，+q所受的电场力为F．则P点的电场强度为（） A . B . C . D . 答案：A,D The picture of the park ________ memories of our class trip last year, when Mr．Smith began to take charge of our class． [　　] A． called up B． reminded C． turned up D． came up