Which of the following devices is used for separating fluids by spinning a vessel at high speed?

The device used for separating fluids by spinning a vessel at high speed is a centrifuge. When a centrifuge operates, it generates a strong centrifugal force that causes denser components of a mixture to move outward, while lighter components remain nearer to the center. This principle is often applied in laboratories and clinics to separate blood components, such as plasma and red blood cells, or to clarify solutions.

Each of the other choices serves different purposes. An autoclave is specifically designed for sterilization using steam under pressure, making it essential for ensuring that surgical instruments and materials are free of pathogens. A microscope is utilized for magnifying small objects or organisms, allowing for detailed examination of specimens, but it does not perform any fluid separation. An endoscope is a tool used to visualize the interior of a hollow organ or cavity, primarily for diagnostic or surgical purposes, rather than for the separation of fluids. Hence, the centrifuge is the correct answer for fluid separation by rapid spinning.