**Sluice Valve in Water Distribution System**

The correct answer to the question is option 'A', which is a sluice valve.

**Definition and Purpose of a Sluice Valve:**
A sluice valve, also known as a gate valve, is a type of valve that is commonly used in water distribution systems. It is a linear motion valve that is designed to control the flow of water by sliding a gate or wedge across the path of the fluid. The gate or wedge is raised or lowered by a threaded stem, which is connected to a handwheel or actuator.

**Function of a Sluice Valve:**
Sluice valves are installed in water distributing pipes at street corners and pipe junctions to control the flow in the distribution system. They are primarily used for the following purposes:
1. Flow Control: Sluice valves are used to regulate the flow of water in the distribution system. By opening or closing the valve, the flow rate can be adjusted as required.
2. Isolation: Sluice valves are used to isolate certain sections of the distribution system for maintenance or repair purposes. When a section needs to be shut off, the sluice valve is closed to stop the flow of water to that specific area.
3. Prevention of Water Hammer: Sluice valves are effective in preventing water hammer, which is a hydraulic shock that can occur when the flow of water is suddenly stopped or changed direction. By gradually closing the valve, the water flow can be controlled and water hammer can be minimized.
4. Emergency Shut-off: Sluice valves are also used as emergency shut-off valves. In case of a pipe burst or any other emergency situation, the valve can be closed quickly to stop the flow of water and prevent further damage.

**Advantages of Sluice Valves:**
- Sluice valves have a simple and robust design, which makes them suitable for heavy-duty applications.
- They provide a tight shut-off, ensuring minimal leakage when closed.
- Sluice valves offer low friction loss, allowing for efficient flow of water.
- They have a long service life and require minimal maintenance.

In conclusion, the valve provided in the water distributing pipes at street corners and pipe junctions to control the flow in the distribution system is a sluice valve. It is used for flow control, isolation, prevention of water hammer, and emergency shut-off. Sluice valves have a simple design, provide a tight shut-off, and have a long service life.