What is the common measurement unit for molarity?

Molarity is defined as the concentration of a solution expressed in terms of the amount of solute (in moles) per volume of solvent (in liters). Specifically, it indicates how many moles of a solute are present in one liter of solution. Thus, the correct answer, moles per liter, accurately represents the concept of molarity, highlighting the relationship between the amount of substance (moles) and the volume of the solution in which it is dissolved.

Other options do not align with the definition of molarity. Grams per liter measures mass concentration, which is not the same as molarity, as it does not account for the number of moles. Moles per cubic meter is another concentration unit that, while valid, is less commonly used than moles per liter in most chemical contexts and can lead to more complex calculations. Moles per gallon is also a valid unit, but it is not the standard measurement for molarity, which favors the liter as its base unit for volume.