Answer:
D. The light bulb will be on
Step-by-step explanation:
When a bulb is placed at D it works like a load and will draw the current. The circuit will remain open until the switch B is closed. Once B is closed, the current will start flowing through the bulb and it will turn on.
It can be understood through an experiment as will. You can connect a small LED with a battery and see for yourself that the LED turns on.