Gate valve is best described as:

• A. Non-return valve with flap
• B. Globe valve with threaded stem
• C. Butterfly valve
• D. Control valve with a solid plate operated by a handle and screw mechanism. Rotating the handle moves the plate into or out of the waterway.

Answer: (D)

Gate valves work by sliding a solid plate (the gate) into or out of the flow path. The plate is attached to a threaded stem connected to a handle or wheel; turning the handle raises or lowers the plate. When the plate is lowered, it seats against the valve body to stop flow, and when raised, the bore becomes clear for nearly unobstructed flow. This design provides a tight shutoff and is ideal for on/off control, though it’s not meant for throttling. The other options describe different valve types (check valve with a flap, globe valve with its distinct mechanism, or a butterfly valve), which is why the description of a solid plate moved by a screw mechanism best fits a gate valve.