Final answer:
The acceptable range for a PR Interval on an ECG is between 3 to 5 little boxes, which indicates a normal duration of 0.12 to 0.20 seconds from the start of atrial depolarization to the beginning of the QRS complex.
Step-by-step explanation:
The acceptable range for a PR Interval in ECG readings is b) Between 3 to 5 little boxes. The PR interval is an important part of an electrocardiogram (ECG), which measures the time from the beginning of atrial depolarization (the P wave) to the initiation of the QRS complex. Each small box on the ECG represents 0.04 seconds, and a normal PR interval ranges from 0.12 to 0.20 seconds, corresponding to 3 to 5 small boxes.
An interval shorter or longer than this range could indicate certain heart conditions. For example, a prolonged PR interval is seen in first-degree heart block, while a shortened PR interval may be associated with conditions like Wolff-Parkinson-White syndrome.