Final answer:
A stethoscope is used to listen to the brachial pulse, particularly during blood pressure measurement with a sphygmomanometer.
Step-by-step explanation:
When listening to the brachial pulse, the correct tool to use is a stethoscope. This device is part of a blood pressure measurement system that also includes a sphygmomanometer, which is an inflatable cuff and pressure meter. The procedure involves wrapping the cuff around the upper arm, inflating it to stop blood flow, and then slowly releasing the air while listening with a stethoscope for the sound of blood flow, known as Korotkoff sounds. These sounds help determine systolic and diastolic blood pressure.