Polychlorinated biphenyls (PCBs) which cause environmental exposure risk have these important properties
A. Very high volatility in air
B. Chemically unstable and highly reactive
C. Heat stable and have no flash or fire point
D. Highly soluble in water and poorly soluble in oils and organic solvents
Answer: Option D
Ozone depletion is caused by the increase in the level of
A. Water vapour
B. Chlorofluro carbon (CFC)
C. Oxygen
D. Carbon monoxide
Which of the following is a beneficial activity of microorganisms?
A. Some microorganisms use carbon dioxide
B. Some microorganisms provide nitrogen for plant growth
C. Some microorganisms are used in sewage treatment
D. All the above
Which of the following parameters indicates the organic pollution of a water sample?
A. pH
B. Turbidity
C. Hardness
D. COD
The chemical system for removal of the ions of level of salt is called
A. Ion transfer
B. Ionization
C. Ion exchange
D. Ion vaporization
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