Answer:
D, all of the above.
Explanation:
The right activity is important so that you don't hurt yourself doing something too strenuous.
Your need to know the exercise in order to not get hurt. Technique is very important to prevent injury.
Training in sensible locations means that:
If you hurt yourself, you can get help.
You have enough space to perform an exercise.
You have the right surroundings to perform an exercise (you wouldn't do a flip onto concrete).
