A fire on board a vessel can be extinguished by removing which of the following elements?

To extinguish a fire, it is essential to eliminate one of the three key elements of the fire triangle, which comprises heat, fuel, and oxygen (air). By removing fuel, which is one of the primary components required for a fire to sustain itself, you can effectively stop the combustion process.

In the context of a fire on a vessel, fuel typically refers to any combustible materials present, such as gasoline, oil, or even the boat's structure if it’s flammable. By cutting off the supply of fuel, you prevent the fire from continuing to burn and spread, thereby ensuring safety on board.

The other elements in the fire triangle—heat and air—are also vital to sustain a fire, but removing them is not as straightforward in all situations. Water can be used effectively to cool down a fire and reduce heat, while removing air is often impractical in an open environment. Therefore, focusing on cutting off the fuel source is a straightforward and effective method for extinguishing a fire.