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The World Health Organisation recommends 60 minutes of excersize a day, 5 days a week.
I think the answer may be chosen from simply going through each answer and using common sense.
In my opinion, the answer is "A. E<span>xercise increases oxygen supplies throughout the body, which helps in the handling of stress." Reason(s) for picking this answer: It gives an educated answer to WHY it handles stress.</span>