13. The __________________ they made at school will last through their life. (friend) 14. Their uncle did some __________________ in Rome last year. (sightseer) 15. The students have done the exercises __________________. (easy) 16. Liz found the journey __________________. (enjoy) 17. Tuan is one of the most famous___________________in the world. (environment) 18. The air is__________________polluted by exhaust fumes me from cars. (serious) 19. Tet is one of the most important ________________for Vietnamese people . ( celebrate ) 26. There have been more floods because of _________________ . ( forest ) 27. Jogging is a very _____________form of exercise . ( energy ) 28. I think the careless drivers should be fined ___________. ( heavy ) 29. That program is very __________. None of us likes it . ( bore ) 30. Air ____________can cause a lot of respiratory problems . ( pollute )