Awave with a height of 10 feet and wavelength of 20 feet has a wave base of

10 ft

The wave base of a wave is the depth at which there is no more perturbation of the medium caused by the wave. The wave base of a wave is determined to be half the wavelength of the wave itself.

Therefore;

Wave base = wavelength/2

                   = 20 ft/2

                  = 10 ft

10 feet

Explanation: I got it right on the test (Apex)

the answer is d. 74.02