Concept:Selection reduces genetic diversity, which can make crops more vulnerable to pests.
Explanation:In crop improvement, selection involves choosing plants with desirable traits for propagation.
This repeated selection narrows the gene pool over generations.
A narrow gene pool means plants lack genetic variation.
Without variation, crops have less natural resistance to new or changing pests.
Therefore, they become more susceptible to pest attacks.
This is a key limitation of the selection method.
Answer:D. increases the susceptibility of crops to pests.