What is the metric unit used to measure engine displacement?

The metric unit used to measure engine displacement is liters (L). Engine displacement refers to the total volume of all the cylinders in an engine and is a crucial parameter in determining the engine's size and capacity. In the metric system, volume is commonly expressed in liters, which allows for a standardized way of comparing different engines.

Using liters as the unit of measurement simplifies communication and comparison in technical specifications, especially in regions where the metric system is predominantly used. This unit provides a clear indication of the engine's potential for power and performance.

Other options represent different measurements; gallons and cubic inches relate to volume as well, but they are not part of the metric system. Horsepower measures power output rather than displacement, making it irrelevant to the specific question about engine capacity.