Fill in the blanks with the correct answer.
1. When waste matter ( ) , poisonous and flammable gases are
2. The microorganisms which disintegrate dead plants, animals and other organic waste are called ( ) .
3. The rubbish that is collected must be burnt in incinerators or placed
in ( ) .
4. Smoke and gases from factories cause ( ) pollution.
5. Air and water pollution can cause ( ) .