A

In this question, we analyze an alternating current (AC) system where the current and voltage alternate in direction and magnitude.
Step 1: In an AC circuit, the current and voltage waveforms are sinusoidal. For a complete cycle of AC, both voltage and current pass through zero twice: once when the waveform rises to a peak and once as it falls back to zero.
Step 2: Since the current and voltage become zero 2f times within one second, we note that this corresponds to the frequency 'f'. Therefore, for a frequency of 'f', there are 2 complete cycles in one second.
Step 3: Each cycle involves two transitions to zero per cycle: one while increasing and one while decreasing. Thus, a frequency of f leads to 2f transitions to zero.
Therefore, the explanation confirms the relationship between current, voltage, and frequency. Hence, the behavior described is consistent with standard AC theory.
The answer to the question is correct, and knowing that current and voltage pass through zero at 2f times in one second indicates that the system operates at a frequency 'f' which yields a matching scenario in alternating sources. Thus, we conclude the answer must be confirming the alternating nature of the current and voltage with respect to frequency f.