Question

Which sentence(s) can serve as the concluding statement(s) for the given paragraph?
A. Large reductions in the ozone layer, which sits about 15–30 km above the Earth, take place each winter over the polar regions, especially the Antarctic, as low temperatures allow the formation of stratospheric clouds that assist chemical reactions breaking down ozone.
B. Industrial chemicals containing chlorine and bromine have been blamed for thinning the layer because they attack the ozone molecules, making them break apart.
C. Many offending chemicals have now been banned.
D. It will still take several decades before these substances have disappeared from the atmosphere.

• A. D
• B. B \& D
• C. A \& D
• D. A \& C

Hint:

A strong conclusion can either restate the key phenomenon in a summarizing way or provide a forward-looking implication — sometimes both are needed.

Answer 1

The Correct Option is C

Sentence A works as a concluding remark if the paragraph builds up to explaining the phenomenon and ends by reinforcing where and how the reductions occur. Sentence D also works as a conclusion because it projects into the future, explaining how long the problem will persist even after corrective actions.
Together, A and D provide both closure on the phenomenon and forward-looking context, making option (C) correct.
Sentences B and C serve more as supporting information rather than conclusive remarks.