The phase lag produced by transportation relays

The correct answer is: C. Increases linearly with frequency.

The phase lag produced by transportation relays is a function of the frequency of the input signal. The higher the frequency, the greater the phase lag. This is because the relay takes a finite amount of time to switch from one state to the other, and this time delay increases with frequency.

Option A is incorrect because the phase lag is not independent of frequency. Option B is incorrect because the phase lag is not inversely proportional to frequency. Option D is incorrect because the phase lag does not decrease linearly with frequency.