19. Such unhygienic conditions encourage the spread of diseases. A. decline B. stability C. decrease D. increase 20. Deforestation is one of the biggest environmental threats to the ecological balance in the world. A. sureties B. certainties C. dangers D. safety 21. As fossil fuel resources are running out, it is important for the government to find some types of alternative energy. A. irreplaceable B. substitute C. impossible D. practical 22. Local people have cut down the forests to make way for farming. A. allow farming to take place B. lose way in farming C. have a way of farming D. give way to farming 23. Because farmers had been informed about the bad effects of chemical fertilisers, they started using them sparingly on their farms. A. carelessly B. moderately C. recklessly D. irresponsibly