ANS:D - molecular weights.

Avogadro's law, which I mentioned earlier, provides the foundation for understanding why the statement is true. Avogadro's law states that equal volumes of gases, at the same temperature and pressure, contain the same number of molecules. This law essentially establishes a proportional relationship between the volume of a gas and the number of molecules it contains when temperature and pressure are constant. The molecular weight of a gas is defined as the mass of one mole of the gas. A mole of any substance contains Avogadro's number of particles, which is approximately 6.022×10^23 particles per mole. For gases, this translates to Avogadro's number of molecules per mole. Since equal volumes of gases contain the same number of molecules, comparing the volumes of different gases at the same temperature and pressure allows us to indirectly compare their molecular weights. If we take the same volume of different gases under identical conditions, the gas with the higher molecular weight will have a higher mass. This concept is fundamental in various areas of chemistry and physics, including gas stoichiometry, gas laws, and kinetic theory.