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(a) Algal bloom is caused due to enrichment of water with nutrients such as nitrogen and phosphorus. As the fertility increases plant life increases.

(b) Water becomes unfit for aquatic fauna because of less oxygen, scum and unpleasant odour.

(c) Eutrophication.

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A. FALSE
B. TRUE
C. TRUE
D. FALSE
E. TRUE

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 Motor vehicles equipped with catalytic converter should use unleaded petrol because lead in the petrol inactivates this catalyst and renders it useless.

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Ozone layer as protective layer. The ozone layer in the stratosphere is very useful to human beings because it absorbs the major part of harmful ultraviolet radiation coming from the sun. Therefore, it is called protective layer.
However, it has been observed that the ozone layer is getting depleted. One of the reasons for depletion of ozone layer is action of chloroflorocarbons(CFCs) and aerosol spray propellants. These compounds react with ozone gas in the atmosphere thereby depleting it. If the ozone layer in the atmosphere is significantly decreased, these harmful radiations would reach the earth and cause many damages such as skin cancer, genetic disorders in man and other living forms. 

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Ahmed Khan a plastic sack manufacturer of Bangalore, found an ideal solution to the problem of increasing plastic waste. His company developed Polyblend, a fine powder of recycled modified plastic. The raw material for creating Polyblend was any plastic film waste. The polyblend mixture was mixed with the bitumen and was used to lay roads. In collaboration with R.V.College of Engineering and the Bangalore City Corporation, Ahmed Khan proved that blends of Polyblend and bitumen, when used to lay roads, enhanced the bitumen’s water repellant properties, and helped to increase road life by a factor of three. Using Khan’s technique, by the year 2002, more than 40 kms of road in Bangalore has already been laid. Thus decresing the amount of plastic waste to a great extent.