Solution: The answer is (a) volt-ampere
The apparent power of an electrical circuit is measured in volt-amperes (VA), which is the unit of measurement. A watt-second (also spelled watt-second, symbol W s or W. s) is a derived unit of energy equal to one joule. It is denoted by the symbol W s or W. s. Planck’s constant is measured in joules per second, which is the joule-second.