using cloth napkins rather than paper towels drying clothes on a clothesline on sunny days keeping appliances plugged in when not in use using incandescent light bulbs in the lamps
I gave my students this multiple choice question: Which of the following will reduce a home electric bill?

Only one answer is correct among these 4 choices:
- using cloth napkins rather than paper towels
- drying clothes on a clothesline on sunny days
- keeping appliances plugged in when not in use
- using incandescent light bulbs in the lamps

Could you tell me which one is correct?

drying clothes on a clothesline on sunny days