Together, the esophagus, stomach, and intestines are part of a

They are part of the digestive system. I'm not sure if that is what you were asking for though

The two answers are static and awkward postures.

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)