Ozone is a very toxic gas and a strong oxidizing agent. It is still useful for life on earth :

1. because it traps harmful UV-rays.

2. because it balances global warming.

3. because it traps harmful X-rays.

4. because it  traps harmful $\mathrm{\gamma }$-rays.

Mercury, aluminum, lead, copper, DDT, etc. are an example of :

1. Biodegradable Pollutant.

2. Non-biodegradable pollutant.

3. Non pollutant.

4. Noise pollutant.

A farmer was told that fishes were not fit for human consumption because a large amount of pesticides had accumulated in the tissues of fishes. This happens:

1. By the transfer of pesticides in the food chain.

2. By the degradation of pesticides.

3. By the reaction of pesticides with atmospheric oxygen.

4. By the reaction of pesticides with atmospheric carbon dioxide.

The best alternative of tetrachloroethane for dry cleaning is-

1. Liquified CO₂ along with suitable detergent.

2. Liquified CO₂ along with suitable oil.

3. Liquified SO₂ along with suitable detergents.

4. Liquified SO₂ along with suitable oil.

Which, of the following, gases contributes  nearly 50 % to the green house effect (which, in turn, causes global warming) ?

1. SO₂

2. SO₃

3. CO₂

4. Water vapour

The chemical that is an excellent ‘green’ solvent as well as a greenhouse gas is: 

1. Methanol

2. CFCs

3. Carbon monoxide

4. Carbon Dioxide

Pollution that occurs in the lowest layer of the atmosphere is :

1. Stratosphere pollution.

2. Ozone layer pollution.

3. Air pollution.

4. Troposphere pollution.

Match the terms given in Column I with the compounds given in Column II.

Codes

Biochemical oxygen Demand value less than 5 ppm indicates a water sample to be : 

1. Highly polluted.

2. Poor in dissolved oxygen.

3. Rich in dissolved oxygen.

4. Not suitable for aquatic life.

Living in the atmosphere of CO is dangerous because it : 

1. Combines with O₂ present inside to form CO₂

2. Reduces organic matter of tissues.

3. Combines with haemoglobin and makes it incapable to absorb oxygen.

4. Dilutes the blood.