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
Causes of water-hammer pulse  are 
Select and explain. 
A. Truncus arteriosus, B. Patent ductus arteriosus, C. Both, D. None
C: Both
Answer: C: Both 
Explanation: Water hammer pulse (collapsing pulse) is seen in:

Hyperkinetic circulatory states
Aortic regurgitation
Patent ductus arteriosus 
Truncus arteriosus with truncal sufficiency