Definition: You are given a question on clinical knowledge. You are also given 4 answer options (associated with "A", "B", "C", "D"), out of which only one is correct. You need to answer the question by selecting the correct option. You should only answer with the choice letter, not the whole answer.
Input: What is cardiac output?
(A)Stroke volume × heart rate. (B)Systemic vascular resistance × heart rate. (C)Blood pressure × heart rate. (D)Preload × stroke volume.

A