Indicates the volume of blood moving during a particular time.

• A. Stroke volume
• B. Flow
• C. Cardiac output
• D. Flow velocity

Answer: (B)

Flow is the rate at which blood volume moves through a vessel or system, expressed as volume per unit time (for example, mL per minute). The question asks for the quantity that indicates how much blood is moving during a given time, which matches this idea of flow.

Flow differs from flow velocity, which is about speed (distance per time) rather than how much volume is moving. Stroke volume is the amount of blood ejected with each heartbeat (per beat), while cardiac output is the total blood volume pumped into the circulation per unit time, i.e., the overall flow of blood through the system. The description points to flow as the best match because it directly describes volume over time.