If at the rate at which a disturbence is made is doubled, what what is the effect on the period, frequency, amplitude, and wavelength of a wave?

by definition , frequency is the rate at which disturbance is made through a medium. hence when rate at which disturbance is made doubled, the frequency also gets doubled,

Time period is given as

T = 1/f                      where T = time period , f = frequency

so when frequency is doubled , Time period becomes half , since Time period is inversely related to the frequency.

Amplitude does not depend on frequency hence amplitude remains unchanged .

wavelength is given as

λ = v/f

Wavelength becomes half when the frequency is doubled since wavelength is inversely related to frequency and speed is constant.

the answer would be a