Which activity is primarily a cardio exercise?

• A. Running.
• B. Weightlifting.
• C. Stretching.
• D. Yoga.

Answer: (A)

Cardio exercise, or aerobic training, is about sustaining rhythmic activity that raises and maintains the heart rate to improve endurance. Running fits this best because it uses large muscle groups in a continuous, steady pace, typically for several minutes, which keeps the heart and lungs working harder. Weightlifting focuses on short, intense efforts to build strength, with rest periods between sets, so the heart isn't maintained at cardio levels. Stretching is for flexibility and range of motion and doesn’t significantly elevate heart rate, while yoga can improve flexibility and mindfulness and may not maintain a high cardio demand. So, running is the primary cardio activity.