NEET Practice Questions (MCQs) with Answers & Solutions

3).

CO2—also known as greenhouse gases—has become a major concern as climate change becomes a bigger issue. China is the world's largest contributing country to CO2 emissions—a trend that has steadily risen over the years—now producing 9.8 billion metric tons of CO2

Lead emitted from the vehicular exhausts is a harmful pollutant because it persists in the environment as dust for an indefinite time period. It is a major air pollutant in urban areas. Anaemia, weakness, kidney failure, neurological disorders are the symptoms of lead poisoning in humans. Children are more prone to lead poisoning than adults. Hence, the correct answer is 'Lead'.

Lichens represent the symbiotic association between the species of Algae and Fungi. These forms absorb much of their mineral nutrients from the air rather than the soil. So, any contamination would threaten their existence. If air is polluted with sulphur dioxide, then lichens will die in that particular environment. Since the era of industrialization, many species of lichens have gone extinct. Due to this property, lichens are considered to be the indicators of the air pollution. Hence, the correct answer is Usnea (Lichen)'

BOD refers to the biological oxygen demand by the microbes to decompose the organic matter present in the water body. Oxygen enters the water through diffusion and water has the highest potential to hold oxygen. The high temperature, untreated sewage having biotoxins, hazardous waste can reduce the oxygen to an alarming level leading to the hypoxia in fishes, whereafter enduring at the maximum level they die resultantly. This occurs because the untreated sewage is rich in organic matter and microbes utilize the dissolved oxygen for the decomposition.

Acid rain is caused by large scale emission of nitrogen oxides (NOx​), sulphur oxides (SOx​), volatile organic carbon and HCl from thermal power plants, industries and automobiles. Oxides of nitrogen and sulphur combine with water and oxygen and form nitric acid and sulphuric acid, respectively. Thus, option D is correct.

Soil conservation is a method of protecting soil from getting eroded either by wind or by water.

• Few soil conservation methods include:
• Graduated terrace steps which are commonly used to farm on hilly or mountainous terrain. Terraced fields decrease both erosion and surface runoff.
• Wind breaks: Row of trees or a fence, wall, or screen that provides shelter or protection of soil from the wind.
• Conservation tillage is a method of preparing soil from getting eroded. This technique involves leaving the previous year crop residues until the next crop is planted.

“Soil conservation is the prevention of soil loss from erosion or reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination.