In rooms where there are multiple lights, a parallel circuit is better.
In a series circuit, if one light broke, all of the lights would turn off, as the circuit would be broken.
However, in parallel, if one bulb broke, the circuit could still be complete through the other bulbs, so they will stay on.
The answer would be C. 5m
This is because to find d, you would need to divide W (125 J) by F (25 N).
Hope this helps!