Final answer:
The frequency of the tuning fork that takes 2.50 x 10⁻³ s to complete one oscillation is 400 Hz.
Step-by-step explanation:
The frequency of a tuning fork is the number of oscillations it completes in one second. To find the frequency of a tuning fork that takes 2.50 x 10-3 s to complete one oscillation, we take the reciprocal of the time taken:
Frequency = 1 / Time Period
Frequency = 1 / (2.50 x 10-3 s) = 400 Hz.
Therefore, the correct answer is c) (400 Hz).