Given the number of oscillations a wave completes in a period of time, you can determine the amplitude. wavelength. frequency. equilibrium.

The answer is; frequency

One period is the time taken for a particle in a wave to make a complete cycle, for example from one distinct  point in the phase to the exact same point again. The period can be used to infer the frequency of the wave. The shorter the time it takes to complete this cycle, the higher the frequency of the wave. This is given by the following equation;

T = 1/f

b is the best answer for this question.

the scientific method.