After a copper smelter begins operation, local downwind populations of plants begin to adapt to the resulting air pollution. scientists document, for example, that the acid tolerance of several plant species has increased significantly in the polluted area. this is an example of:

a) stabilizing selection.
b) disruptive selection.
c) genetic drift.
d) directional selection.

Directional selection

Explanation:

In the population genetics, directional selection is the mode of selection during which the extreme phenotype are favored more than the other phenotype.

This causes the allele frequency to shift towards the time in the direction of that particular phenotype.

Here, in the question the acid tolerant plant species is favored over the other phenotype.

Hence, the correct answer is option D

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