The correct answer is B. Coulomb.
An ampere is a unit of electric current, not electric charge. The coulomb is the SI unit of electric charge. It is named after Charles-Augustin de Coulomb, a French physicist who studied electricity and magnetism. One coulomb is equal to the charge transported by a constant current of one ampere in one second.
The esu, or electrostatic unit, is a unit of electric charge that is no longer used in the SI system. It was originally defined as the charge of one proton. However, it was later found that the charge of a proton is not exactly one esu. Therefore, the esu was replaced by the coulomb, which is a more accurate unit of electric charge.
The kelvin is a unit of thermodynamic temperature. It is named after Lord Kelvin, a Scottish physicist who developed the Kelvin scale of temperature. One kelvin is equal to one degree Celsius on the Celsius scale.