Final answer:
The correct answer option 1) is a vent pipe, which is used in plumbing to maintain air pressure and prevent vacuum formation that can slow down water drainage.
Step-by-step explanation:
The correct answer is option 1) Vent pipe. A vent pipe is part of a plumbing system that allows air to enter the plumbing system to maintain proper air pressure to ensure the free movement of water through the drainage pipes. This prevents a vacuum from being formed in the system that could potentially slow down the draining of water. A vent pipe ensures that the water in the sink drain flows quickly and efficiently by allowing air to follow the water down the drain, which helps to speed up the water flow and prevent a vacuum. The other options listed do not serve the purpose of providing free movement of air above the flow line of the drain in the same way a vent pipe does.
A horizontal drain that is sized to provide free movement of air above the flow line of the drain is called a vent pipe. Vent pipes are important in plumbing systems as they allow air to enter the drain and prevent the formation of a vacuum, allowing water to flow smoothly through the drain.