UGC NET Questions (Paper – 1)

Statement D is the only wrong statement because ozone layer depletion clearly affects human health and ecosystems through increased UV exposure. Statements A, B and C correctly describe the role of CFCs and halons, protective function of the ozone layer and the purpose of the Montreal Protocol. Increased UV-B can cause skin cancer, cataracts and harm to phytoplankton and terrestrial plants. Therefore, the combination that identifies D alone as wrong is the correct answer.

Option A:
Option A is correct because it isolates statement D as the single wrong statement while recognising that A, B and C are scientifically well established. It reflects the consensus that ozone depletion has serious consequences for health and ecosystems. This option therefore matches the requirement to select the wrong statement or statements.

Option B:
Option B is incorrect because it treats both A and D as wrong. Statement A is correct since CFCs and halons are classic ozone-depleting substances identified in atmospheric chemistry studies. Misclassifying A as wrong shows a misunderstanding of the basic cause of ozone depletion.

Option C:
Option C is incorrect as it considers B and D to be wrong together. Statement B is in fact correct because the ozone layer’s filtering of UV radiation is a fundamental part of atmospheric science. Including B among wrong statements makes this combination unacceptable.

Option D:
Option D is incorrect because it treats C and D as wrong. Statement C accurately summarises the main purpose of the Montreal Protocol, which is a key treaty in global environmental governance. Since only D is wrong, combining it with C produces an incorrect option.

Statements A, B, C, E and F are correct because they describe the protective function of ozone, uses of CFCs, the role of the Montreal Protocol, the need to evaluate substitutes and the slow recovery timeline. Statement D is false since ozone depletion increases UV-B reaching the surface, leading to health effects like skin cancer and cataracts and harming ecosystems. Therefore, the combination that includes A, B, C, E and F while excluding D is correct.

Option A:
Option A is incorrect because it omits E and F and therefore does not mention the importance of evaluating substitutes or the time scale of recovery, which are critical aspects of current ozone discussions.

Option B:
Option B is correct as it covers both historical causes and ongoing management challenges, while rejecting the claim that depletion has no health or ecological consequences.

Option C:
Option C is incorrect since it includes D, which denies well-established effects of increased UV-B, and thus mixes false information with correct statements.

Option D:
Option D is incorrect as it leaves out B, so it fails to state the central role of CFCs in causing ozone depletion, even though that is a foundational example in the unit.

Stratospheric ozone is depleted when chlorine and bromine atoms, released from certain man-made chemicals, catalyse reactions that destroy ozone molecules. Chlorofluorocarbons (CFCs), halons and some related halogenated compounds are particularly important sources of these atoms. They are stable in the lower atmosphere but break down under strong UV radiation in the stratosphere, releasing ozone-destroying radicals. Consequently, these substances are recognised as the main cause of the ozone hole, making option C correct.

Option A:
Option A is incorrect because sulphur dioxide and nitrogen oxides are more closely associated with acid rain and tropospheric pollution. They do not play the dominant role in stratospheric ozone depletion.

Option B:
Option B is incorrect since carbon dioxide and methane are key greenhouse gases driving climate change, but they do not directly cause the ozone hole. Climate change and ozone depletion are related but distinct problems.

Option C:
Option C is correct as CFCs and similar compounds were widely used in refrigeration, aerosols and foam blowing. Their regulation under the Montreal Protocol has led to gradual recovery of the ozone layer.

Option D:
Option D is incorrect because oxygen and nitrogen are natural components of the atmosphere and are essential in forming and maintaining the ozone layer. They are not pollutants responsible for its depletion.