Answer:
Plant species that have increased their tolerance to acid in the presence of environmental contaminants is an example of a response to directional selection (option e).
Explanation:
Directional selection favors a specific trait within some individuals in the population, because they develop greater biological efficiency or have adapted better to environmental changes.
If a graph is made according to the characteristic of "acid tolerance" -where perhaps few plants are tolerant- the presence of a contaminated environment will favor the reproduction and survival of acid-tolerant plants, making resistant plants more frequent in the graph.
Because environmental conditions change, when the change persists over time, an inherited trait -such as acid resistance- is favored, making the population with this trait more frequent.
Learn more:
Differences between directional selection and disruptive selection brainly.com/question/10519034