What is used to connect a 2 ½ hose to a 1 ¾ hose?

The correct choice is a reducer. In the context of firefighting equipment, a reducer is specifically designed to connect hoses of different diameters. For instance, in this scenario, the reducer allows the firefighter to connect a 2 ½ inch hose to a 1 ¾ inch hose, accommodating the difference in size. This capability is essential for maintaining water flow and pressure when longer runs of hose are required, facilitating effective firefighting operations.

A connector typically refers to a fitting used to join two hoses of the same size or type, while an adapter serves a similar function but often can match different threads or coupling types rather than diameters. Couplings are generally used to attach hoses of the same diameter, not to transition between different sizes. Understanding the specific roles of each component is crucial for effective equipment use in firefighting situations.