ANS:A - temperature.

The osmotic pressure of a dilute solution of a non-volatile solute in a solvent obeying Raoult's law is proportional to the: "Mo​les of non-volatile solute." Osmotic pressure (𝜋π) is defined by the equation: 𝜋=𝑀𝑅𝑇π=MRT Where:

• 𝑀M is the molarity of the solution (moles of solute per liter of solution),
• 𝑅R is the ideal gas constant (0.0821 L atm / mol K or 8.314 J / mol K),
• 𝑇T is the absolute temperature in Kelvin.

For a dilute solution, the molarity (𝑀M) can be approximated by the mole fraction of the solute (𝑥x), and Raoult's law states that the vapor pressure of the solution is proportional to the mole fraction of the solvent (𝑃=𝑥𝑃⋆P=xP⋆, where 𝑃⋆P⋆ is the vapor pressure of the pure solvent). Since osmotic pressure is related to the concentration of particles in the solution, it's directly proportional to the number of moles of the solute dissolved in the solution. Therefore, the correct answer is: "Mo​les of non-volatile solute."