That would be the nervous system.
Answer:
1. disease involving abnomalities present at birth: congenital
2. arteries that feed the heart: coronary
3. the growth of abnormal cells: cancer
4. when the body is unable to use the hormone insulin: diabetes
Explanation:
Say you get bullied and want to be home schooled :)
The least likely explanation for this would be that they're training at different intervals, or one is training harder than the other.
The most likely reason is that the way the other person's genetics are most people cant gain muscle as well as others because of disease or their body structure.
Hope this helped!
