A:甲
B:乙
C:丙
D:丁
两点电荷间距离为r时,相互作用力为F,当距离变为r/2时,它们之间相互作用力为____F,为使作用力仍为F,则两点电荷的电量可同时为原来的____倍.
— Would you like to go for a picnic with me?
— ______ I have to help Kate with her Chinese