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: Physiology
Pulmonary vasodilatation is caused by ? 
Select and explain. 
A. Hypoxia, B. Thromboxane A2, C. Histamine, D. Angiotensin-II
C: Histamine
Answer: C: Histamine 
Explanation: Ans. is 'c' i.e., Histamine