Flow of water in a pipe about 3 meters in diameter can be measured by

Answer: Option D

Flow measurement in large diameter pipes, such as a 3-meter diameter water pipe, requires devices that can handle high flow rates and provide accurate readings with minimal energy loss.

An orifice plate causes significant head loss and is more suitable for smaller pipes.

A rotameter is typically used for low flow rates and smaller pipe diameters in vertical applications.

A pitot tube can measure velocity at a point but is not practical for measuring total flow in such a large pipe.

The venturi meter is specifically designed to measure flow in large pipes. It operates on the principle of pressure differential and causes minimal energy loss.

Therefore, for a pipe about 3 meters in diameter, the most suitable device is the venturi meter.

Correct answer is Option B: venturi