Explanation
Atmospheric pollutants like carbon particles and smoke from factories harm the plants. They can have direct toxic effects, or indirectly by changing soil $$pH$$ followed by solubilization of toxic salts of metals like aluminum. The particular matters have a negative mechanical effect. They cover the leaf blade reducing light penetration and blocking the opening of stomata. These impediments influence the process of photosynthesis whose rate declines sharply.
Option B is correct.
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