1. Tidal energy is renewable, ______plentiful______and clean. (plenty)
2. Wind will be used as an _____enviromental (adj )_______friendly sources of energy. (environment)
3. There are many ways will be used to solve the problem of ______pollution (N)_______. (pollute)
4. Solar power can be used to _____heat_______or cool our houses. (hot)
5. _______unfortunately (không may là) ________, fossil fuels are harmful to the environment. (fortunate)
6. We should use them_____economical (tiết kiệm )____ and try to find out alternative sources of power. (economy)
7. Solar energy is___renewable (tái tạo)_________, plentiful and clean. (renew)   
8. I think that solar energy can be an______alternative (thay thế )_____ source of energy in the near future. (alter)
9. We should reduce the use of_____electricity______ at home. (electrical) 
10. It’s a clean source of energy. Sailboats couldn’t move without this____power____. (powerful)
11. Waves will be used as an _____environmental____friendly sources of energy (environment)