Electron volt is a unit of

The electron volt (symbol ev; also written electronvolt) is a unit of energy equal to approximately $\left.1.602 \times 10^{-19} \text { joule (SI unit } \mathrm{J}\right)$

By definition, it is the amount of energy gained by the charge of a single electron moved across an electric potential difference of one volt.

Hence, the correct option is $d$