Which one is correct regarding electrocardiograph (ECG)?
A. P-wave represents the electrical excitation of the ventricle.
B. QRS complex represents repolarization of the ventricles.
C. T-wave represents repolarization of the atria.
D. By counting the number of QRS complexes one can determine the pulse rate.

Hint: Electrocardiography is the process of obtaining a chart of voltage versus time showing the electrical movement of the heart, and the diagram is known as an electrocardiogram (ECG). In this , the electrical potential of a human heart is estimated from twelve distinct points and recorded over a period of time that can be 10 seconds.

Complete answer:
Electrocardiography is the procedure for obtaining an electrocardiogram. It is a graph of the voltage versus time of the electrical action of the heart using anodes placed on the skin.
The P-wave addresses the electrical excitation (or depolarisation) of the atria, which causes both atria to compress. The QRS complex addresses ventricle depolarization, which initiates ventricular contraction. The pinnacle of the QRS complex can be used to calculate an individual's heartbeat. The top of the QRS complex in an ECG shows one heartbeat. The T-wave addresses the transition of the ventricles from a state of eagerness to a state of normalcy (repolarisation). As a result, by counting the number of QRS structures that occur in a given time period, one can determine a person's heart rate.

Hence, the correct answer is option B. QRS complex represents repolarization of the ventricles.

Note:
EP, or cardiovascular electrophysiology, is the study of the heart's conduction system. It is a right-side cardiovascular catheterization in which a wire with a cathode at the tip is inserted into the appropriate heart chambers. It is placed in various positions in the conduction framework so that its electrical movement can be recorded.