Answer : The unit of electric potential or electromotive force is volt.
Explanation :
Electric potential is defined as the work done in moving a charge from one reference point to a particular point in the presence of any field. It is also know as Electromotive force or EMF.
It is also termed as voltage. Its SI unit is volt.
1 Volt is defined as one joule per coulomb.
Hence, the correct option is (a) " volt ".