Choose the correct answers.
1. The wind, the sun, and the wave are some types of……………..sources of energy.
2. Remember to……………the lights before going to bed.
3. By the middle of 21st century, people in developing countries………....more renewable energy.
4. Fossil fuels are very common in our society but they...……the environment.
5. The governments try to………….the use of fossil fuels.
6. We should put…………….on our roof for the heating and hot water.
