Which material is s common indoor air pollutant? smog natural gas vehicle exhaust oxygen

I’m pretty sure it’s smog or vehicle

The answer is smog that's the material in air pollutant

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)