[单选题]
The energy acquired by a particle carrying a charge eq u-e7wm)(luo n(czax.ual to that on the ele qudm5pjp2*- vctron as a result of moving through a potential difference of one volt is referq*2-jdu vpp m5red to as
A. a joule.
B. an electron-volt.
C. a proton-volt.
D. a coulomb.