1. We must use electricity .................................. ( economy ) 2. ....................... energy is the best alternative source of energy ( sun ) 3. Some volunteer .............................. are cleaning up the beach ( conserve ). 4. .................. is better than cure ( prevent ) 5. A good body and love from our parents are the most ......................... thing I have ( price). 6. These toys made in the USA is ............... to children ( harm ) 7. Food is a ............... of our life ( need ). 8. No doubt there will be a great .......................... of food for the world's population ( short ). 9. I am .................... disappointed to know my children have not cleaned up all the trash ( extreme ). 10. Neighbors ............................. to the police about the noise from that house last night ( complaint ) 11. White ao dai symbolizes the .................... of the girl students ( pure ) 12. Smoking does harm ............................... to people's health ( repair ). 13. Speaking in pubic seems to come quite ............................ to her ( nature ). 14. We are looking forward to the latest .......................... in computer technology ( innovate ). 15. ...................................., you will have to make the decision yourself ( ultimate ). 16. The lava in the volcano ........................... as it cools ( solid ). 17. Paper and most plastics are ............................. materials ( recycle ). 18. What should you do at school to ................................. pollution ! ( minimum )