Answer: B. eV
eV, also known as electron-volt, is the measure of the quantity of kinetic energy gained by an electron accelerating through an electric potential difference of one volt from rest through a vacuum. The SI unit of power is a watt, which equals one joule per second. Some other traditional measures however are adopted to serve as units of power. They include calories per hour, horsepower, kilowatt, joule per second, foot-pounds per minute, etc.