What type of instrument is used to measure blood pressure?

A sphygmomanometer is specifically designed to measure blood pressure, making it the correct choice for this question. This instrument typically consists of an inflatable cuff that is wrapped around the upper arm and a gauge that displays the pressure reading in millimeters of mercury (mmHg). When the cuff is inflated, it compresses the arteries, and as the cuff deflates, the healthcare provider listens for specific sounds (usually with a stethoscope) that indicate the systolic and diastolic blood pressures.

Other instruments mentioned in the choices serve different purposes. A stethoscope is used to listen to heartbeats and other bodily sounds but does not measure blood pressure itself. A thermometer is used to measure body temperature, and a pulsometer measures pulse rate rather than blood pressure. Thus, the unique function of the sphygmomanometer in directly measuring blood pressure sets it apart as the correct answer.