To measure static pressure in a pipe, one uses a pressure gauge connected to a pilot tube. The pilot tube is a small tube that is inserted into the pipe and connected to the pressure gauge. This setup allows for accurate measurement of the static pressure in the pipe.

The pilot tube works based on the principle of Bernoulli's equation, which states that the total pressure in a fluid system is constant. In a pipe, the total pressure is made up of the static pressure and the dynamic pressure.

When the pilot tube is inserted into the pipe, it is positioned in such a way that it is perpendicular to the flow of the fluid. This allows it to measure only the static pressure of the fluid.

The pressure gauge connected to the pilot tube measures the pressure difference between the fluid in the pipe and the fluid in the pilot tube. By subtracting the pressure in the pilot tube from the pressure in the pipe, the static pressure can be determined.

Using a pilot tube to measure static pressure has several advantages:

1. Accuracy: The pilot tube allows for accurate measurement of the static pressure as it is not affected by the dynamic pressure or the velocity of the fluid flow.

2. Non-intrusive: The pilot tube is inserted into the pipe without obstructing the flow of the fluid. This ensures that the measurement is not affected by any disturbances in the flow.

3. Versatility: The pilot tube can be used to measure static pressure in pipes of various sizes and shapes. It can also be used in both liquid and gas flow systems.

In contrast, the other options mentioned in the question - venturi meter, orifice meter, and pitot tube tapping - are used to measure the total pressure or the dynamic pressure in a pipe. They are not suitable for measuring static pressure alone.

Hence, the correct answer is option A - pilot tube.