Final answer:
Cardiac output is the volume of blood pumped by the heart per minute and is determined by stroke volume and heart rate. The correct composition of cardiac output is stroke volume and heart rate.
Step-by-step explanation:
Cardiac output is the volume of blood that the heart pumps in one minute. It is composed of two main factors: stroke volume (SV) and heart rate (HR). These two variables can be manipulated to alter blood flow and blood pressure. An increase in cardiac output can be achieved by increasing either the stroke volume, the amount of blood pumped by the ventricle during each heartbeat, or the heart rate, the number of heartbeats per minute. Likewise, a decrease in stroke volume or heart rate will reduce cardiac output, influencing blood pressure and blood flow correspondingly.
The correct answer to the student's question would therefore be: Cardiac output is composed of B. stroke volume and heart rate.