Directional selection only occurs in response to naturally occurring events.

False.

Explanation:

Directional selection is a form of natural selection and occurs in response to the existence of extreme phenotypes in a population and not in response to naturally occurring events.

An example of directional selection can be seen when a population of flies has small, large and medium-sized individuals. Larger flies are easily hit by spraying insecticides. Thus, small flies have a great advantage over large and medium flies. In this way, small flies are more likely to survive and reproduce, causing a directional selection.

the answer is a or when it says crossing over

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