A battery, a switch S, and four identical lightbulbs A, B, C, and D are arranged in a circuit as shown above.
How does the current in lightbulb A change, if at all, when the switch is closed, and why?
A It does not change because the closed path through the battery and lightbulbs A, B, and C has not changed.
B It increases because the equivalent resistance of parallel lightbulbs C and D is less than the resistance of lightbulb D.
C It decreases because the current now passes through both lightbulbs C and D as it travels clockwise around the circuit.
D The currents cannot be compared without knowing the values of the resistances and the battery's potential difference.