Physical exercise and fresh air are effective stress management techniques because:
This is a 2-mark question, so two clear points suffice. Examiners expect you to mention specific activities (yoga, meditation, deep breathing, walking/playing) and their direct benefits (blood circulation, relaxation, fresh oxygen, increased activeness). Avoid vague statements like "exercise is good" — link the activity to its benefit.
Source: Chapter 2, Session 1 — Stress Management, Management Techniques