Which of the following risks is the least likely to affect an individual who has been smoking for only a few months?
a.
lung cancer
b.
shortness of breath
c.
yellowing teeth
d.
reduced sense of smell

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)

Iwould put 'think' in the blank