Answer: The right answer is -
A) Gene flow 
Explanation:
Gene flow is a process of gene migration or the transfer of gene variant (also called allele, which is responsible for genetic variation in population) from one population to another population.
As a consequence of gene migration, new alleles are introduced or added in the already existing population, thereby increasing genetic diversity. 
Thus, option A) is the right answer. 
 
        
             
        
        
        
I would say,
Aa.
Please mark brainlist.
And sorry for the user below ..☺☻
 
        
             
        
        
        
Answer:
This is considered as the study of homology.
Explanation:
Homology, studies the comparable characteristics of the physiology, structure or development of various species based on their decent from a similar evolutionary ancestor.
 
        
             
        
        
        
Answer:
The correct answer will be-
1. decrease in blood volume
2. secretion of renin from juxtaglomerular apparatus
3. production of angiotensin II
4.  secretion of aldosterone
5. sodium reabsorbed from distal tubules and collecting ducts
Explanation:
The RAAS pathway or Renin-angiotensin II-aldosterone pathway gets activated in the human body to maintain the osmolarity and blood volume.
When the receptors in the blood sense the low volume of water in the body sends signals to the brain which activates the secretion of the renin from the juxtaglomerular cells. Renin helps converts the inactive angiotensin to angiotensin I and II which help reabsorption of sodium ions. This activates the production of aldosterone which increases the reabsorption of the sodium ions into distal and collecting ducts.
 
        
             
        
        
        
A recessive allele is shown in the phenotype