Conservation is the act of guarding, preserving and protecting. So conserving will help reduce air pollution because instead of letting thing go to the wrong garbage or whatever you can save and conserve and even reuse. decreases air pollution.
Sprinting is an anaerobic form of exercise
All of the above is your answer
Likely the chronological age, mainly because it would explain the differences in puberty stages between the two boys, which is an example of physical maturation.
