Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: Vasconstricts systemic arterioles: 
 Options:  <1> Low pO2. <2> Low pH. <3> Angiotensin II. <4> Acetylcholine <5> Nitric oxide.
