A cock valve is used to:

A cock valve is specifically designed to quickly allow or stop the flow of fluid within a piping system. Its primary function is to act as a straightforward on/off switch for flow, making it ideal in situations where immediate control is necessary. By turning the valve handle, an operator can rapidly close or open the passage, effectively managing the flow without the need for adjusting pressure, temperature, or conducting flow measurements. This quick-response capability is particularly useful in applications where safety and efficiency are paramount, allowing for immediate action to prevent potential hazards or manage processes effectively.

The other functions—regulating pressure, controlling temperature, and measuring flow rate—are typically managed by different types of valves or instruments that perform those specific tasks with precision, rather than a simple on/off mechanism like that of a cock valve. Hence, the primary role of the cock valve as a flow control device highlights why it is correctly identified in this context.