What is the necessary instrument for measuring blood pressure? (A. Sphygmomanometer B. Stethoscope C. Sphygmomanometer and tourniquet D. Sphygmomanometer and stethoscope. )

It must be a sphygmomanometer and a stethoscope. The sphygmomanometer generally displays the blood pressure value with a mercury column, and the stethoscope is used to listen to the blood pressure value. When you hear the first sound, it is systolic pressure, and when the continuous tone weakens (commonly known as inflection), it is diastolic pressure. But if you use an electronic sphygmomanometer, you don't need a stethoscope.