10.(c) A 20W-low energy will take an incredible 50 hours to consume 1kWh of electricity; replaced old-style 100W bulb would replace it in only 10 hours.
10.(c) A 20W low-energy bulb will take an incredible 50 hours to consume 1kWh of electricity; the old-style 100W incandescent bulb it replaced would do it in just 10 hours.