Final answer:
The equipment used for the prevention of blood clots is the Sequential compression device.
Step-by-step explanation:
The piece of equipment used in the prevention of blood clots is c) Sequential compression device. This medical device applies gradual pressure to the legs and then deflates, mimicking the natural blood flow and movement, thereby helping to prevent blood clots in patients who are immobile. Other options listed such as a) Sphygmomanometer, are used to measure blood pressure, b) Tourniquet, which is used to control bleeding, and d) Stethoscope, which is used to listen to the internal sounds of the body, do not serve the purpose of preventing blood clots.