A coulomb is a unit of electric charge in the International System of Units (SI). It is named after the French physicist Charles-Augustin de Coulomb and is defined as the amount of electric charge carried by a constant current of one ampere in one second.
Therefore,
option 2 - "Unit of electricity that contains a certain amount of electrons" is not an accurate description of a coulomb.
Option 1 - "Measurement used to rate electrical pressure in a circuit" and
option 3 - "Unit of electricity that indicates both quantity and time" are partially correct, but a coulomb is primarily a unit of electric charge.
Option 4 - "Measurement used to rate the power usage of an output device" is not related to a coulomb.