Photochemical smog was first observed in -

(1) London

(2) Los Angeles

(3) Paris

(4) Tokyo

An increase in ${\mathrm{CO}}_2$ concentration in the atmosphere will result in : 

1. Adverse effects on natural vegetation.

2. Global warming.

3. Temperature decrease in a global atmosphere.

4. Genetic disorders in plants and animals.

Domestic waste will lead to -

(1) Biodegradable pollution

(2) Nondegradable pollution

(3) Thermal pollution of soil

(4) Air pollution

The major source of BOD in the river Ganga is 

(1) Leaf litter

(2) Fishes

(3) Human waste

(4) Aquatic plants

If a lake is contaminated with DDT, its highest concentration would be found in

(1) Primary consumer

(2) Secondary consumer

(3) Tertiary consumer

(4) None of these

The most harmful air pollutant produced by automobiles is- 

1. ${\mathrm{HNO}}_2$

2. NO

3. ${\mathrm{SO}}_2$

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 : 

(1) The amount of $O_2$ utilized by organisms in the water .

(2) The amount of $O_2$ utilized by microorganisms for decomposition .

(3) The total amount of $O_2$ present in water .

(4) All of the above . 

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