What principles focuses on working the core muscles first and then works other muscles? a)concentration b)mind over matter c)centering d)precision

The principle focuses on working the core muscles first and then works other muscles is Precision.  Exercises should be performed with precision and focus. Details matter much. Working with precision will affect the muscles that you work and the effectiveness with which you work them. Failing to focus on the precise details will reduce the effectiveness of the method.

well i’m not to well in health but if the body produces more standard fat then the fat will convert most of it into energy and give all the muscles nutrients (sorry if it was wrong  

b) the heart is a pump made of muscle and that is difficult to grow in the lab.