Under what conditions, do molar volumes of different gasees contain equal number of molecules ?

What is condition for molar Volume ?

Under similar conditins of T and P, equal volumes of all gases contain equal number of molecules'. This statement is given by

Equal volume of all gases always contains equal number of moles.

Equal volumes of all gases contain equal number of _________.

Assertion (A) : 22.4 L of nitrogen at S.T.P and 5.6 L of oxygen at S.T.P contain equal number of molecules . Reason (R) : Under similar condition of temperature and pressure all gases contain equal number of molecules .

Name the law in Physics which states that equal volume of all gases under the same conditions of temperature and pressure contain equal numbers of molecules.