Q.5 World's most problematic aquatic weed is

1. Azolla

2. Wolffia

3. Eichhornia

4. Trapa

Q.6 Which of the following causes biomagnification?

1. ${\mathrm{SO}}_2$

2. Mercury

3. DDT

4. Both (b) and (C)

The expanded form of DDT is

1. dichloro diphenyl trichloroethane

2. dichloro diethyl trichloroethane

3. dichloro dipyridyl trichloroethane

4. dichloro diphenyl tetrachloroacetate

The green scum seen in the freshwater bodies is

1. blue-green algae

2. red algae

3. green algae

4. Both (a) and (c)

Which one of the following diseases is not due to contamination of water?

1. Hepatitis-B

2. Jaundice

3. Cholera

4. Typhoid

Nuisance growth of aquatic plants and bloom-forming algae in natural
water is generally due to high concentrations of

1. carbon

2. sulfur

3. calcium

4. phosphorus

Q.20 Algal blooms impart a distinct color to water due to

1. their pigments

2. excretion of colored substances

3. formation of colored chemicals in water facilitated by the physiological degradation of algae

4. absorption of light by algal cell wall