“男女同姓, 其生不蕃”的意义()
A.兄弟姐妹不许通婚
B.婚配要遵守社会道德风俗
C.避免近亲婚配,利于优生
D.同姓男女不能通婚
E.以上都不是
参考答案:C
一带电的粒子射入一固定的点电荷Q形成的电场中,沿图中虚线由a点运动到b点,a、b两点到点电荷的距离分别是ra、rb,且ra>rb,若粒子只受电场力,则在这一过程中( )
A.粒子一定带正电荷
B.电场力一定对粒子做负功
C.粒子在b点的电势一定高于a点的电势
D.粒子在b点的加速度一定小于在a点的加速度
用所给词的适当形式填空
1.The pencil looks as if it ____ (break) with half of it in the glass of water.
2. Li Ming speaks English very well as though he ___ ( be) an Englishman.
3. It seems as if our team ____ (be)going to win.
4. He talks about pyramids as though he ___ (see) themhimself.