This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
In a normal electrocardiogram (ECG or EKG), 
Select and explain. 
A. The P wave results from repolarization of the atria., B. The QRS complex results from depolarization of the ventricles., C. The T wave represents repolarization of the auricles., D. During the P-R interval, the ventricle contract.
B: The QRS complex results from depolarization of the ventricles.
Answer: B: The QRS complex results from depolarization of the ventricles. 
Explanation: B: The QRS complex consists of three individual waves: the Q, R, and S waves. The QRS complex results from depolarization of the ventricles, and the beginning of the QRS complex precedes ventricular contraction.
A: The P wave results from depolarization of the atrial myocardium, and the beginning of the P wave precedes the onset of atrial contraction.
C: The T wave represents the repolarization of the ventricles, and the beginning of the T wave precedes ventricular relaxation.
D: During the P-R interval, the atria contract and begin to relax.