Which among the following is a unitless physical quantity?

The mole fraction of a solute in a binary solution is $0.1$. At $298 \ K$,molarity of this solution is same as its molality. Density of this solution at $298 \ K$ is $2.0 \ g \ cm^{-3}$. The ratio of molecular weights of the solute and the solvent $(M_{solute} / M_{solvent})$ is:

$3.0 \ g$ ethanoic acid in $50 \ g$ benzene has . . . . . . molality. (Atomic weights: $H=1, C=12, O=16$).

If the concentration of $Al^{3+}$ in an aqueous solution of $Al_2(SO_4)_3$ is $0.28 \ M$,then the concentration of $(SO_4)^{2-}$ ion is ........... $M$.

If $5.85 \ g$ of $NaCl$ (molecular weight $58.5$) is dissolved in water and the solution is made up to $0.5 \ L$,the molarity of the solution will be (in $M$)

Assertion $(A)$: Molality of a solution increases with temperature.
Reason $(R)$: Molality expression does not involve any volume term.