The correct answer is: B. Time required to complete one cycle.
A wave is a disturbance that travels through a medium from one point to another. The period of a wave is the time it takes for one complete cycle of the wave to occur. The frequency of a wave is the number of cycles that occur per unit time. The amplitude of a wave is the maximum displacement of the wave from its equilibrium position.
Option A is incorrect because the period and frequency of a wave are different quantities. The period is the time it takes for one complete cycle of the wave to occur, while the frequency is the number of cycles that occur per unit time.
Option C is incorrect because the period of a wave is not expressed in amperes. The period is a measure of time, while amperes are a unit of electric current.
Option D is the correct answer because it is the only option that is consistent with the definition of the period of a wave.