Answer:
f = 2 Hz
Explanation:
The frequency of a wave is defined as the no. of waves passing per unit of time. Therefore, the frequency of a wave can be calculated by the following formula:

where,
f = frequency of the wave = ?
t = time passed = 1 s
n = no. of waves passing in time t = 2
Therefore,

<u>f = 2 Hz</u>
I think the correct answer from the choices listed above is option A. The kinetic energy after the perfectly inelastic collision would be zero Joules. <span>A </span>perfectly inelastic collision<span> occurs when the maximum amount of kinetic energy of a system is lost. Hope this answers the question.</span>