Answer:
D. Bulb 2 will go out but bulbs 1 and 3 will remain lit.
Step-by-step explanation:
If switch at B is opened then, Bulb 2 will go out but bulbs 1 and 3 will remain lit. This is because the positive and negative current flow still fully passes through the two closed switches at switch A and C which allows the bulbs to receive both currents and thus allowing it to turn on. When Switch B is opened it cuts off access for the negative charge to get to bulb 2 and without it, bulb 2 will not turn on.