1. Tidal energy is renewable, ............................ and clean. (plenty)
2. Wind will be used as an ............................ friendly sources of energy. (environment)
3. There are many ways will be used to solve the problem of .................... (pollute)
4. Solar power can be used to ............................ or cool our houses. (hot)
5. ............................, fossil fuels are harmful to the environment. (fortunate)
6. We couldn’t see the airplane because it ......................... behind the cloud.(appear)
7. I don’t think it will come true soon; however, your idea is really ...............(imagine)
8. He feels very tired after two continuous nights of ......................... (sleep
