Given below are two statements: one is labelled as Assertion A and the other…
2023
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Hydrofluorocarbons (HFCs), used as replacements for ozone-depleting chlorofluorocarbons (CFCs), were also decided to be phased out at the 1992 Copenhagen conference.
Reason R: HFCs have shorter atmospheric lifetimes than CFCs and contain neither chlorine nor bromine.
In the light of the above statements, choose the correct answer from the options given below:
Answer: D. A is false but R is true — CONCEPTIn an assertion-reason item, test the truth of each statement independently before testing whether the reason explains the assertion. Treaty dates…
- A.
Both A and R are true and R is the correct explanation of A
- B.
Both A and R are true but R is NOT the correct explanation of A
- C.
A is true but R is false
- D.
A is false but R is true
Attempted by 1 students.
Show answer & explanation
Correct answer: D
CONCEPT
In an assertion-reason item, test the truth of each statement independently before testing whether the reason explains the assertion. Treaty dates establish policy chronology, while molecular composition and atmospheric lifetime establish the chemical claim.
APPLICATION
The 1992 Copenhagen Amendment accelerated controls on ozone-depleting substances such as CFCs and added controls on other halogenated substances; it did not establish the HFC phase-down.
The global phase-down of HFC production and consumption was adopted much later through the Kigali Amendment to the Montreal Protocol in 2016.
HFC molecules contain hydrogen, fluorine and carbon but no chlorine or bromine, so they have zero ozone-depletion potential. Their hydrogen-containing structure generally makes them more reactive in the lower atmosphere and shorter-lived than fully halogenated CFCs.
CONTRAST
Both A and R are true, with R explaining A: this requires Assertion A to be true, contrary to the treaty chronology.
Both A and R are true, without R explaining A: this also requires Assertion A to be true, contrary to the treaty chronology.
A is true but R is false: this reverses both independent findings from the treaty and chemical evidence.
A is false but R is true: this matches the independent treaty-timing and chemical-composition checks.
CROSS-CHECK
The treaty chronology makes Assertion A false, while the chemical comparison makes Reason R true.
Result: A is false but R is true.