Which statement best describes the normal heart rate on an ECG based on the R-R interval 3-5 large boxes?

Which statement best describes the normal heart rate on an ECG based on the R-R interval 3-5 large boxes?

• A. Normal rate is defined by irregular R-R interval.
• B. Tachycardia is defined by R-R interval of 3-5 large boxes.
• C. Bradycardia is defined by R-R interval of 3-5 large boxes.
• D. Normal rate is defined by R-R interval between 3 and 5 large boxes.

Answer: (D)