Final answer:
The average normal heart rate for a healthy adult at rest is between 60-100 bpm, making 72 bpm the correct answer.
Step-by-step explanation:
The average normal heart rate for a healthy adult at rest is typically within the range of 60-100 beats per minute (bpm). Therefore, the correct answer to the question is b. 72 beats per minute. Bradycardia is a condition where the heart rate is less than 60 bpm, which might not be a concern for well-trained athletes but could be a medical concern for others. It is crucial for our body's circulatory system to maintain an adequate heart rate to supply blood to vital tissues effectively.