$P = \large \frac {dRT}{M} \Rightarrow \frac{P}{d} = \frac{RT}{M} $$\rightarrow$ depends only on T for a given gas.

$u = nC_v T\rightarrow$ depends on number of moles and T.

$PV = nRT \rightarrow$ depends also on number of moles.

Therefore, the correct answer is (A) ratio of pressure and density of the gas.