Answer:
The correct answer is - The adaptive value of allele b increased.
Explanation:
In this given population of insects, there is an increase in the number of insects in the given time of five years as initially there were 2800 insects and after five years there are 4000 insects, however, it is not the most probable explanation for the change in the phenotype as phenotype change does not depend on the size of population alone.
In this case, there is a drastic increase in the number of the recessive allele in last five years that suggests that adaptive value is increased of recessive allele due to some environmental change or mutation in the gene.
