UGC NET Questions (Paper – 1)

Statements A, B, D, E and F are all correct and together explain which gases are important, how the enhanced greenhouse effect works and how radiation is trapped. Carbon dioxide is the main long-lived anthropogenic gas, methane is more potent per unit mass, water vapour is a feedback gas and greenhouse gases absorb outgoing longwave radiation. Statement C is false because nitrous oxide and many fluorinated gases are well-known greenhouse gases with significant warming effects. Therefore, the combination that includes A, B, D, E and F only is correct.

Option A:
Option A is incorrect because it leaves out F and therefore fails to mention the basic physical mechanism of longwave absorption by greenhouse gases. Without F, the explanation of how warming actually occurs remains incomplete.

Option B:
Option B is correct as it lists all the true statements and excludes only C, which denies the greenhouse role of nitrous oxide and fluorinated gases. It provides a conceptually coherent description of greenhouse gases and the enhanced greenhouse effect.

Option C:
Option C is incorrect since it includes C, which is demonstrably wrong, and omits B, thereby losing the point about methane’s higher warming potential. This mixture of errors and omissions makes it unsuitable as the correct answer.

Option D:
Option D is incorrect because it omits A, ignoring the central role of carbon dioxide, while also excluding A’s emphasis on the primary anthropogenic driver. It also contains only a subset of true statements and thus does not fully characterise greenhouse gas behaviour.

Greenhouse gases are those that can absorb and emit infrared radiation, contributing to the greenhouse effect. Carbon dioxide from fossil fuels and deforestation, methane from agriculture and waste, and nitrous oxide from fertilisers are key anthropogenic drivers of current climate change. They have increased significantly in concentration since the industrial revolution.

Option A:
Option A is incorrect because nitrogen, oxygen and argon are major components of air but are not strong greenhouse gases under normal conditions.

Option B:
Option B is correct as it lists three important long-lived greenhouse gases recognised in international climate agreements.

Option C:
Option C is incorrect since neon, helium and krypton are inert gases with negligible greenhouse effect.

Option D:
Option D is incorrect because hydrogen, neon and argon are not principal contributors to observed warming.