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100 questions in this collection · Page 10 of 10
Question 91 of 100
📘 CLASS XII
Environmental Issues
Analyze the following statements about Biochemical Oxygen Demand (BOD):
I. High sewage concentration in water corresponds to a high BOD value. II. Decomposing microbes consume oxygen, causing a sharp drop in dissolved oxygen (DO). III. A drop in dissolved oxygen leads to heavy mortality among fish and other aquatic life. IV. Downstream from the sewage discharge point, BOD rises as water self-purifies.
Which of the statements given above are correct?
Statement IV is incorrect because as self-purification proceeds downstream, biodegradable organic matter decreases, causing BOD to decline while dissolved oxygen gradually recovers.
Question 92 of 100
📘 CLASS XII
Environmental Issues
Consider the following statements regarding Algal Blooms:
I. Nutrients like nitrates and phosphates stimulate the excessive growth of planktonic algae. II. Algal blooms impart a distinct, often bright green or red color to the water. III. Algal blooms improve the taste of drinking water and make it safe for consumption. IV. Some bloom-forming algae produce toxins that are deadly to animals and humans.
Which of the statements given above are correct?
Algal blooms occur due to nutrient enrichment, discolor water, deteriorate water quality and may release toxic substances harmful to humans and animals. Statement III is therefore incorrect.
Question 93 of 100
📘 CLASS XII
Environmental Issues
Read the following statements regarding the "Terror of Bengal":
I. It refers to the water hyacinth (Eichhornia crassipes). II. It is an aquatic weed introduced to India for its beautiful flowers and leaf shapes. III. It grows faster than our ability to clear it, choking aquatic life by draining oxygen. IV. It thrives exceptionally well in clean, nutrient-deprived mountain lakes.
Which of the statements given above are correct?
Statement IV is incorrect because water hyacinth flourishes in nutrient-rich, eutrophic and polluted water bodies, not in clean nutrient-poor mountain lakes.
Question 94 of 100
📘 CLASS XII
Environmental Issues
With reference to the process of Biomagnification, read the following statements:
I. Biomagnification refers to an increase in toxicant concentration at successive trophic levels. II. The toxicant accumulates because it cannot be metabolized or excreted. III. The concentration of DDT starts in water at a level of 0.003 ppm. IV. High concentrations of DDT interfere with calcium metabolism in birds, leading to premature eggshell breakage.
Which of the statements given above are correct?
Statement III is incorrect because the initial concentration of DDT in water is 0.003 ppb (parts per billion), not ppm (parts per million). Statements I, II and IV are correct.
Question 95 of 100
📘 CLASS XII
Environmental Issues
Consider the following statements regarding the Eutrophication of lakes:
I. Eutrophication is the natural aging of a lake by nutrient enrichment. II. In a young lake, the water is cold and clear, supporting very little organic life. III. As organic debris and silt accumulate, the lake grows shallower and warmer. IV. Marsh plants take root in the shallows, eventually turning the basin into land.
Which of the statements given above are correct?
All four statements are correct. Eutrophication is the natural aging of a lake. As silt and organic matter accumulate, the lake becomes shallower and warmer, allowing marsh vegetation to eventually convert the lake basin into land.
Question 96 of 100
📘 CLASS XII
Environmental Issues
Regarding Cultural Eutrophication and Thermal Wastewater, consider the following statements:
I. Pollutants from human activities, like sewage and industrial effluents, accelerate eutrophication. II. This human-accelerated aging process is called cultural or accelerated eutrophication. III. Thermal wastewater from electricity-generating plants reduces the numbers of temperature-sensitive organisms. IV. Thermal wastewater has absolutely no impact on cold-water indigenous species.
Which of the statements given above are correct?
Statement IV is incorrect because thermal wastewater damages or eliminates temperature-sensitive indigenous organisms by raising the water temperature beyond their tolerance limits.
Question 97 of 100
📘 CLASS XII
Environmental Issues
With reference to the integrated wastewater system in Arcata, California, read the following statements:
I. The cleaning process was developed in collaboration with Stanford University. II. Stage one includes conventional sedimentation, filtering, and chlorine treatments. III. Heavy metals are removed by passing the water through six connected marshes over 60 hectares. IV. The marshes are seeded with appropriate algae, fungi, plants, and bacteria.
Which of the statements given above are correct?
Statement I is incorrect because the Arcata project was developed in collaboration with biologists from Humboldt State University, not Stanford University.
Question 98 of 100
📘 CLASS XII
Environmental Issues
Analyze the following statements about Ecological Sanitation (EcoSan) toilets:
I. EcoSan is a dry composting toilet system designed to handle human excreta. II. It is a highly hygienic, practical, and water-saving sanitation alternative. III. Human excreta can be recycled into organic manure, reducing dependence on chemical fertilizers. IV. EcoSan systems are presently non-functional and banned due to health concerns in India.
Which of the statements given above are correct?
Statement IV is incorrect because EcoSan systems are functional and are successfully operating in several areas of Kerala and Sri Lanka.
Question 99 of 100
📘 CLASS XII
Environmental Issues
Consider the following statements regarding Ahmed Khan's plastic waste project:
I. He developed Polyblend, a fine powder of recycled, modified plastic. II. Polyblend is mixed with bitumen to lay roads, enhancing water repellency. III. The blend of Polyblend and bitumen increases road life by a factor of three. IV. Rag pickers were offered Rs 6 per kg for plastic waste, up from the regular Rs 0.40.
Which of the statements given above are correct?
All four statements are correct. Polyblend improves road quality, enhances water repellency, increases road life threefold, and provided rag pickers with a much higher price for plastic waste.
Question 100 of 100
📘 CLASS XII
Environmental Issues
Read the following statements regarding integrated organic farming:
I. Ramesh Chandra Dagar, a farmer in Sonipat, Haryana, practiced integrated organic farming. II. It is a zero-waste, cyclical system where waste products of one process are recycled as nutrients for others. III. He founded the Haryana Kisan Welfare Club, which has a membership of 5,000 farmers. IV. He relies heavily on chemical nitrogenous fertilizers to increase the composting rate.
Which of the statements given above are correct?
Statement IV is incorrect because integrated organic farming eliminates the need for chemical fertilizers. Crop residues and cattle dung are recycled into natural manure in a zero-waste system.