Which statement about blood pressure is true?

• A. It is measured in millimetres of liters.
• B. It is affected by heartbeat, blood volume, and elasticity of vessel walls.
• C. It is measured in grams per square centimeter.
• D. It remains constant regardless of arterial tone.

Answer: (B)

Blood pressure is the force exerted by circulating blood on the walls of arteries and depends on how much blood the heart pumps with each beat (cardiac output) and the resistance and elasticity of the arterial system. The statement is true because the heartbeat drives the pressure during each contraction, blood volume sets how much fluid is pressing outward, and the elasticity of vessel walls determines how easily arteries expand in response to that pressure. Units matter here too: blood pressure is measured in millimetres of mercury (mmHg), not litres or other unit types. Arterial tone also affects pressure, so it is not constant regardless of tone.