Use the words to complete the sentences below.

1. Excessive use of ... ... causes air pollution.

2. Using sticky traps instead of ... ... can help reduce pollution.

3. ... ... , that live in carpets and mattresses, are known to cause allergies.

4. If you want to be sure to keep the air in your house fresh, you need to clean or replace your ... ... regularly.

5. Some doctors believe that having a cat in the home is the cause of ... ... for many people.