Which of the following are most suitable indicators of SO₂ pollution in the environment?
1. Lichens
2. Conifers
3. Algae
4. Fungi

A location with luxuriant growth of lichens on the trees indicates that the:

1. Trees are very healthy

2. Trees are heavily infested

3. Location is highly polluted

4. Location is not polluted

There exists a close association between the alga and the fungus within a lichen. The fungus:

Lichens can be used as:
1.  Bio-indicator for water and air pollution
2.  Initial vegetation for waste lands
3.  Source of wood
4.  To check the air pollution