Impeller is the ...

• A. Outer ring
• B. Round disk
• C. Hollow core
• D. Nut and bolt assembly

Answer: (B)

An impeller is the rotating round disk with blades that moves and accelerates fluid inside a pump. As it spins, the blades push fluid outward, increasing its velocity and pressure and transferring mechanical energy from the motor to the fluid. That makes “round disk” the best description. The other options describe parts that aren’t the impeller itself: an outer ring is part of the housing, a hollow core isn’t the defining feature of the impeller, and a nut and bolt assembly are fasteners used to hold components together.