Correct option is
C 1 Joule/Coulomb
– Volt is the electrical unit of voltage or potential difference (V).
– $\mathrm{V}$ is related to Change in Potential Energy $\Delta \mathrm{U}$ as
$$
\mathrm{V}=\frac{\Delta \mathrm{U}}{\mathrm{q}}
$$
From above formula, We get 1 Volt potential difference when a change of 1 joule of Potential energy is there in moving a charge of 1 Coulomb.
Therefore, 1 Volt $=1$ Joule/Coulomb.