This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Physiology
Whenever availability of oxygen to tissues decreases immediately 
Select and explain. 
A. Vasodilation and increase in blood supply to tissue takes place, B. Vasoconstriction and decreases in blood supply to tissue takes place, C. Venoconstriction and increase in tissue perfusion pressure occurs, D. Venodilation and decrease in tissue perfusion pressure occur
A: Vasodilation and increase in blood supply to tissue takes place
Answer: A: Vasodilation and increase in blood supply to tissue takes place 
Explanation: Vasodilator Theory for Acute Local Blood Flow Regulation Possible Special Role of Adenosine. According to this theory, the greater the rate of metabolism or the less the availability of oxygen or some other nutrients to a tissue, the greater the rate of formation of vasodilator substances in the tissue cellsRef: Guyton 11th edition pg no: 196