Answer: E. all of the above.
Explanation: for human infants to grow and develop normally, the need for them to interact with people (family, friends and the public) cannot be over emphasized. Interaction with people goes a long way in the brain, physical and social development of infants.
Frequent interaction with people helps infants in their communication skills.
Option D would be that answer
The source is the allele for beak size being different, or more specifically the DNA sequences being different.
The isolation barriers prevents two of the species to mate, resulting in them evolving into different species
