[单选题]
The net work done in tpx;.ssb.l7g moving an electron from point A, where the potential .g,gl1j 4zkw.wqa0w zis -50 V, to point B, where the pot .,04a1lzqz .ggkw wwjential is +50 V, is
A. $+1.6 \times 10^{-17} \; J$.
B. $-1.6 \times 10^{-17} \; J$.
C. zero.
D. none of the given answers
