To find the average current in an inductor, we need to consider the concept of reactance in an inductor. Reactance is the opposition offered by an inductor to the flow of alternating current (AC).

When an AC current flows through an inductor, it creates a magnetic field around the inductor. This magnetic field stores energy in the form of electromagnetic fields. As a result, the current in an inductor is not in phase with the applied voltage. The current lags behind the voltage by 90 degrees in an ideal inductor.

The reactance (X) of an inductor is given by the formula:

X = 2πfL

Where:
- X is the reactance of the inductor in ohms (Ω)
- π is a mathematical constant approximately equal to 3.14
- f is the frequency of the AC current in hertz (Hz)
- L is the inductance of the inductor in henries (H)

The average current in an inductor is given by the formula:

Iavg = Imax / √2

Where:
- Iavg is the average current in the inductor in amperes (A)
- Imax is the maximum current in the inductor in amperes (A)

In this case, the total current in the inductor is given as 30A. Therefore, the maximum current (Imax) is also 30A.

Using the formula for average current:

Iavg = 30A / √2

Calculating the value of Iavg:

Iavg ≈ 30A / 1.414

Iavg ≈ 21.213A

So, the average current in the inductor is approximately 21.213A.

Therefore, none of the given options (a), (b), (d) are correct.

The correct answer is option (c), 15A.