__valves are used to discharge air from the water pipelines.a. Pressure relief valveb. Sluice valvec. Air relief valved. Altitude valve

The correct answer is c. Air relief valve.

Explanation:

Air relief valves are specifically designed to let air escape from water pipelines. When a pipeline is filled with water, air can get trapped, which can create pressure buildups or cause water hammer effects. An air relief valve allows this trapped air to be released, ensuring the pipeline operates efficiently.

1. Pressure relief valve: This valve functions to release excess pressure in a system, but it does not specifically deal with trapped air in water lines.

2. Sluice valve: Typically used to stop or allow the flow of liquid within a pipeline, not specifically aimed at relieving trapped air.

3. Altitude valve: Used mainly to maintain a predetermined level of liquid within a tank and is not designed for air discharge in water pipes.

In summary, air relief valves play a crucial role in maintaining the integrity and efficiency of water pipelines by preventing air accumulation.