题目

Had it been at all possible, I would have gone to attend her in the hospital, but I ________ fully occupied last week. A. was       B. had been     C. am       D. have been 答案：A某电场中的一条电场线为直线，a、b为这条直线上的两点，如图所示 （　　）A．a点的场强一定大于b的场强B．a点的电势一定高于b点的电势C．把一负点电荷由b点从静止释放，在不计重力的情况下，一定向a点做匀加速直线运动D．一负点电荷从a点向b点运动过程中，它的电势能一定增加