Chlorofluorocarbons (CFCs), important greenhouse gases, A. are toxic B.…

Concept

The environmental behavior of a chlorofluorocarbon follows from two linked properties: physical volatility determines how it is used near ambient temperature, while chemical stability lets it persist long enough to reach the stratosphere.

Many common CFC refrigerants are low in acute toxicity and nonflammable. In the stratosphere, ultraviolet light releases chlorine radicals, which catalytically destroy ozone.

For exam-style environmental science items, these traits refer to common commercial CFCs under standard refrigerant-safety classifications; they are not universal zero-risk claims at every concentration.

Application

• Statement A: in the standard safety classification used for refrigerants, common CFCs have low acute toxicity and were not treated as toxic substances in this statement set; this does not mean harmless at every dose.

• Statement B: CFC-11 boils at about 23.7 degrees Celsius, just below a conventional room temperature of 25 degrees Celsius. Other CFCs have different boiling points, so B is the exam’s representative-property shorthand.

• Statement C: CFCs are generally nonflammable, another reason for their former use as refrigerants and propellants.

• Statement D: strong carbon-halogen bonds make CFCs very stable in the lower atmosphere.

• Statement E: after stratospheric photolysis, chlorine radicals participate in ozone-destroying catalytic cycles.

Cross-check

The official UGC NET convention rejects A and C because common commercial CFCs are classified as low in acute toxicity and nonflammable. It accepts B through the representative CFC-11 boiling point, D through lower-atmosphere stability, and E through chlorine-catalyzed ozone loss.

Therefore, under the source exam’s intended classification, the supported combination is B, D and E only.