Which phrase best defines stress? a. an autoimmune disorder characterized by “flares” b. a primitive instinct for the body to defend itself c. a collection of unexplained physical problems d. a condition characterized by delusions and confused thinking

D. a condition characterized by delusions and confused thinkig

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)