Complete the crossword puzzle with the help of clues given below:

1. CFCs or Chlorofluorocarbons were used in refrigerators and air conditioners earlier.

2. The ozone layer found in the Stratosphere protects us from harmful UV radiations.

3. Carbon monoxide is produced when incomplete combustion of fuel takes place.

4. Oxygen is required for combustion to take place.

5. Cholera is caused by drinking impure or contaminated water.

6. Pesticides are chemicals that help protect crops from the harmful actions of pests. However, these are harmful and poisonous substances, which when crops are watered, get washed away with it causing water pollution.

7. The Ganga river is famous in India and sustains most of the northern, central and eastern Indian population.