Final answer:
Both equations provided, A. wave speed = frequency x wavelength, and B. wave speed = (1/period) x wavelength, are correct for calculating wave speed since frequency is the inverse of period.
Step-by-step explanation:
The correct equation for wave speed is wave speed = frequency x wavelength. This can also be expressed using the period of the wave (the time it takes for one complete oscillation), since frequency is the reciprocal of the period (f = 1/T). Therefore, the wave speed can also be calculated as wave speed = (1/period) x wavelength. Both A and B options provided in the question are correct. Mathematically, the relationship can be written as v = fλ, where v represents the wave speed, f is the frequency, and λ (lambda) is the wavelength.