This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ECG and Arrhythmia 3, Subject name: Medicine
Feature of Torsades de pointes is? 
Select and explain. 
A. Normal P waves, B. Sho QRS complex, C. Prolonged QTc interval, D. Sho QTc interval
C: Prolonged QTc interval
Answer: C: Prolonged QTc interval 
Explanation: Torsades de pointes/Polymorphic V. Tachycardia-Prolonged QTc interval QTc=''C'' means corrected T wave,as it does not end immediately. T wave goes in slight gradual slope, so we exactly cannot pin point end of the T wave. So to pin point end of T wave ,mathematical scenario called as QTc is used