This process can be defined as the positive selection in which one phenotype is selected over the other phenotype, causing the allele frequency to shift towards the other phenotype.
The allele favored by directional selection is advantageous. There is a increase in the rate of reproduction and chances of survival.
Here, the population of rabbits are decreasing in size over a period of time because they adapted the burrows to live in. Gradually small size of the rabbits were favored.
The correct answer is option C. Endocrine glands secrete hormones into the bloodstream because endocrine glands are ductless and the exocrine glands have ducts so they secrete their hormones into the ducts.
