Which unit is commonly used to measure mass?

The correct answer is kilograms, a unit that is universally recognized in the metric system for measuring mass. Kilograms are used to quantify the amount of matter in an object and are essential in various scientific and engineering contexts. This unit is defined such that one kilogram is equal to the mass of the International Prototype of the Kilogram, a platinum-iridium cylinder stored in France.

Other units listed serve different measurement purposes: lumens measure luminous flux, which relates to light output; milliliters are a measure of volume rather than mass; and acres are used to measure area, commonly in land measurement contexts. Understanding the distinction between these types of measurements clarifies why kilograms is the appropriate choice for measuring mass.