Explanation: This question applies Ohm's Law, a fundamental principle in electronics and amateur radio theory. Ohm's Law describes the relationship between voltage (V), current (I), and resistance (R) in a circuit. It is typically expressed as V = I × R. To find the resistance (R) when voltage and current are known, you can rearrange the formula to: R = V / I Plugging in the given values: R = 90 volts / 3 amperes R = 30 ohms Therefore, a resistance of 30 ohms is required for 3 amperes to flow at 90 volts. Options A, C, and D are incorrect as they do not result from the correct application of Ohm's Law with the provided values.