The human body is made up of several organ systems that work together as one unit. Which organ function to breaks down food into nutrients?

A. kidney

B. heart

C. esophagus

D. stomach

Stomach, The stomach contains acid that helps break down the food.

The person who utilize the progression principle will keep adding the difficulty of the exercise that he's doing, while the person who does not, will only stay stagnant.  the person that utilize progression principle, will get a stronger endurance because now his body is conditioned to do harsher routines.{the answer was already on verified)