Gravity-feed systems are most commonly found at which of the following locations?

Gravity-feed systems utilize the force of gravity to move water from a higher elevation to a lower one, making them most effective and efficient when situated at high elevations. In such systems, water stored in tanks or reservoirs positioned at elevated locations can flow down naturally without the need for mechanical pumps, which saves energy and reduces operational costs. This positioning allows for a reliable water supply that can easily reach lower areas, benefitting firefighting operations where immediate access to water is critical.

The other options do not align with the principles of gravity-feed systems. Low elevations would be less effective for such setups, as there wouldn’t be a gravity advantage to direct the flow of water. Coastal areas and urban centers might have their own systems in place, but they do not inherently necessitate or optimize the use of gravity-feed mechanisms the way high elevation locations do.