Which type of fire hose can be utilized as both an attack line and a supply line?

Answer: C — Medium-diameter hose

The correct answer highlights medium-diameter hose as a versatile option capable of serving as both an attack line and a supply line. Medium-diameter hoses typically have diameters ranging between 2.5 inches (63.5 mm) and 3 inches (76.2 mm), making them suitable for pumping significant volumes of water while still being manageable for fire attack operations. This size allows them to deliver the necessary water flow rate during firefighting efforts and can also be used to supply water to fire apparatus or larger attack lines due to their capability to handle volume and pressure. In comparison, large-diameter hose is primarily designed for use as a supply line, often connecting water sources to pump operations needing a substantial volume of water; it is not typically used for direct attack due to difficulty in maneuverability. Small-diameter hose is generally meant for attack lines due to its lightweight nature but cannot manage the supply requirements of larger operations. High-pressure hoses are specifically tailored for applications requiring elevated pressures and are not standard for typical fireground operations related to both supply and attack lines. Thus, medium-diameter hoses provide a balanced option that meets the diverse needs of firefighting scenarios effectively.