Answer:
D. Power cords to the motherboard are not connected.
Explanation:
The correct option is the power cord that supplies electricity to the motherboard is not connected. The idea that there's no light or sound indicates the system isn't on or booting. The only option there that indicates why the computer may not boot.
Other options available albeit creates a problem for the computer, will still turn on the computer. But if the motherboard doesnt get power, the booting process doesn't start.