Correct Answer - D
We known that from the reaction `H_(2)+Cl_(2) rarr 2HCl` that the ratio of the volume of gaseous reactants and products is in agreement with their molar ratio. The ratio of `H_(2) : Cl_(2) : HCl` volumes id `1 : 1 : 2` which is the same as their number of moles. Therefore, the assertion is false but reasonis true.