This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
Which of the following is not true of "a" wave of venous pulsations in neck? 
Select and explain. 
A. Exaggerated in tricuspid stenosis, B. Abolished in atrial fibrillation, C. Occurs just after in carotid aery, D. Exaggerated in complete hea block when P wave falls between QRS and T waves
C: Occurs just after in carotid aery
Answer: C: Occurs just after in carotid aery 
Explanation: There is no valve at the junction of superior vena cava (SVC) and right atrium (RA) therefore right atrial pressure changes are transmitted to the jugular vein in the neck. "a" wave is due to atrial systole. Some blood regurgitates into the great veins when atria contracts, even though the orifices of IVC and SVC are constricted. In addition veins inflow stops, causing the rise in venous pressure, contributing to the" a" wave.