Four conducting loops each contain the same 100Ω resistor. The situations are as follows:
1. Loop A is connected to a 9 V ideal battery.
2. Loop B is connected to a 3 V ideal battery.
3. Loop C is connected to a 9 V ideal battery, but its switch is open so the circuit is incomplete.
4. Loop D has no battery connected; the resistor forms a closed loop with a length of wire.
Rank the magnitude of the current in the resistor for the four loops from greatest to least.
a) B > A > C = D
b) A = B > C = D
c) A > B > C = D
d) A = C > B > D