Well generally it will be a positive impact (Of course this generally depends on what the "Physical activity" is, it is generally good, reason being while exercising causes the brain to release endorphin's, as well as helping relax muscles and relieve physical tension, which can greatly help with stress.
Some methods of progressive resistance exercise used to improve muscle fitness would be to increase the weight you lift. Do the same amount of reps and sets each week along with that but only increase your weight percentage by 2 or 10 of your RM load at a time. Don’t go overboard.
This is an example of ODD or Oppositional Defiance Disorder.
This is a diagnosis where a child just blatantly disobeys and has issues with being told what to do by anyone; especially authority figures.
The Answer to your question is B that person Is right.