This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
Pulmonary circulation differs from systemic circulation 
Select and explain. 
A. Pulmonary vasodilatation in hypoxia, B. Pulmonary vasoconstriction in hypoxia, C. Decreased blood volume during systole, D. Increased basal vasoconstrictor tone
B: Pulmonary vasoconstriction in hypoxia
Answer: B: Pulmonary vasoconstriction in hypoxia 
Explanation: Hypoxic pulmonary vasoconstriction (HPV), also known as the Euler-Liljestrand mechanism, is a physiological phenomenon in which small pulmonary aeries constrict in the presence of alveolar hypoxia (low oxygen levels). Ref: guyton and hall textbook of medical physiology 12 edition page number: 354,355,356