Final answer:
The quantity of electrical energy used by the electric bulb rated 120 watts used for 3 hours is 360 watt-hours.
Step-by-step explanation:
The electrical energy used by an electric bulb can be calculated by multiplying its power rating (in watts) by the time it is used (in hours).
In this case, the power rating of the bulb is 120 watts and it is used for 3 hours.
To calculate the energy used, multiply the power rating by the time:
Energy = Power x Time
Energy = 120 watts x 3 hours = 360 watt-hours.
Therefore, the quantity of electrical energy used by the bulb is 360 watt-hours (A).