原式=1+3+3+1+3-1=4+23.
真空中两个等量同种电荷电量的值均为q,相距为r,两点电荷连线中点处的场强大小为
A.0
B.
C.
D.
Until the final votes are cast, though, assurances ______ for nothing.
A.count
B.meant
C.give
D.account