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
Canon 'a' waves in JVP represents: March 2007 
Select and explain. 
A. Complete hea block, B. 1st degree A-V block, C. Sinus bradycardia, D. Tachycardia
A: Complete hea block
Answer: A: Complete hea block 
Explanation: Ans. A: Complete hea block