(d) All of the above
Stress management improves mood, boosts the immune system, and promotes longevity, making option (d) correct.
Source: Session 1: Stress Management, Chapter 2
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The passage states that effective stress management helps you "have a joyful life," "be more energetic," and prevents long-term health problems — collectively pointing to improved mood, a stronger immune system, and longer, healthier living. In MCQs where all options are valid benefits, always choose "All of the above."