Which item is commonly used to attach a smaller hose to a larger one?

The reducer is the correct answer because it is specifically designed to connect a smaller hose to a larger hose by effectively reducing the diameter of the larger line to match that of the smaller line. This allows for a secure and effective flow of water from a larger hose to a smaller one without leaks or disruption.

In the context of firefighting, proper equipment and methods for connecting hoses are crucial for efficient water delivery. The reducer serves this function by creating a smooth transition between different hose sizes, which can be necessary for various firefighting scenarios, such as drafting water from a source or extending the reach of a hose line.

While an adapter also connects hoses, it usually refers to a fitting that allows for the attachment of similar-sized hoses or varying types of attachments rather than specifically managing size differences. The coupling is primarily used to connect two hoses of the same size, facilitating continuity in hose lines, while an expander is not typically used in this context, as it would serve the opposite function by transitioning from a smaller diameter to a larger one.