Which of the following examples best classifies as 'exercise' rather than just 'physical activity'?

• A. Standing and shifting weight occasionally while talking on the phone, performed every day but without a structured plan or progressive goals.
• B. A 30-minute planned jog at a steady pace with the intent to improve aerobic endurance.
• C. Unstructured wandering through a museum for 45 minutes without a targeted intensity or intention to improve a fitness component.
• D. Carrying groceries from the car to the kitchen three times a week without any change in intensity or plan and without progressive overload.

Answer: (B)