Statement (A): Vapour density is the ratio of density of gas to density of Hydrogen gas.

Statement (B): Vapour density has no units

Statement (C): $\text{Molecular\hspace{0.17em}mass = 2}\times \text{Vapour Density}$

$\text{Vapour\hspace{0.17em}density (V.D) =}\frac{\text{Density\hspace{0.17em}of gas,gram/cc}}{\text{Density\hspace{0.17em}of Hydrogen , gram/cc}}$$\Rightarrow \text{ no units}$                                           

Note: We always remember that if the units are same in denominator and numerator then units is canceled out just we get numerical values.

 Molecular mass $=2\times vapourdensity$