Final answer:
The capacitor in an LC circuit is fully charged at time t = 0, which is the moment right before the switch is closed to begin energy oscillation between the capacitor and inductor.
Step-by-step explanation:
The student's question pertains to a circuit composed of an inductor (L) and a capacitor (C) forming an LC circuit, and asks at what time, t, is the capacitor fully charged. According to the provided information and the nature of an LC circuit without resistance (since the question does not mention any resistor in the loop), the capacitor starts discharging through the inductor the moment the switch is closed. Since it’s implied that the switch closure occurs at the start of the observation of the circuit's behavior, the correct answer is a. 0, meaning the capacitor is fully charged at time t = 0. This is the moment right before the switch is closed, beginning the oscillation process where energy transfers between the capacitor's electric field and the inductor's magnetic field.