A:Enough
B:Thank
C:Really
D:Rubbish
真空中两个点电荷Q1、Q2,距离为R,当Q1增大到2倍时,Q2减为原来的 13 ,而距离增大到原来的3倍,电荷间的库仑力变为原来的( )
It is a nice picture. Ann _________ it for me.