Which of the following expresses Avogadro's Law?

Avogadro's Law states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules. This law emphasizes the direct relationship between the volume of a gas and the number of molecules (or moles) present, provided the temperature and pressure remain constant. In essence, it allows us to understand that if two different gases occupy the same volume under identical conditions, they must have the same number of molecules, regardless of the types of gases involved.

This concept is foundational in chemistry because it helps in converting between volumes of gases and the number of particles, which is crucial for reactions involving gaseous substances. Therefore, the choice that correctly articulates Avogadro's Law is the one that reflects this principle regarding gas volume and the amount of substance.