If a lake is contaminated with DDT, it's highest concentration would be found in :

1. Primary consumer

2. Secondary consumer

3. Tertiary consumer

4. None of the above.

The most harmful air pollutant produced by automobiles is:

1. $HN{O}_2$

2. $N{O}_X$

3. $S{O}_2$

4. CO

Sewage water can be purified by

(1) Aquatic plant

(2) Microorganism

(3) Penicillin

(4) Fishes

Major pollutant in Jet plane emission is -

(1) $S{O}_2$

(2) CFC

(3) CO

(4) $CC{l}_4$

B.O.D is-

What is the intensity of sound in normal conversation 

1. 10 -20 decibal

2. 30 - 60 decibal

3. 70 - 90 decibal

4. 120 - 150 decibal

Which of the following is absent in polluted water

1. Hydrilla

2. Water hyacinth

3. Larva of stone fly

4. Blue green algae

Maximum green house gas released by which country

(1) India

(2) China

(3) U.S.A

(4) Britain

The ozone layer of the upper atmosphere is being destroyed by : 

1. Sulphur dioxide

2. Carbon dioxide

3. Chlorofluorocarbon

4. Smog

Most hazardous metal pollutant of automobile exhaust is

(1) Hg

(2) Cd

(3) Pb

(4) Cu