Answer:
The correct answer is: physiological hypertrophy.
Step-by-step explanation:
Brian is a young and very healthy young man; as an athlete, the amount of physical effort he engages in is much greater than the amount on non-athletes. For this particular reason, his heart (specifically, his left ventricle, which pumps blood to the aorta for it to reach the his whole body) has begun to enlarge in size, for it to be able to respond accordingly to the highly active lifestyle that he has. This is known as physiological hypertrophy: physiological refers to the normal function of the human body, while hypertrophy means enlargement of one's organs, tissues or cells.