He has no complaints and takes no medications

A 23 year-old man visits his physician for a routine examination. He is an Olympic weight lifter. He has no complaints and takes no medications. His medical, surgical and family histories are unremarkable. His muscles undergo hypertrophy and are capable of performing greater forces.
What is the reason of his muscles’ hypertrophy?
A- Increased length of contractile fibers
B- Increased number of contractile fibers
C- Increased myosin ATPase activity
D- Increased connective tissue content
Answer: https://goo.gl/ksVW3t

Ans B