For a dilute solution of a non-volatile, non-electrolyte solute in a volatile solvent, which statements are correct?

1. AThe relative lowering of vapour pressure equals the mole fraction of the solute.
2. BThe absolute lowering $P^0-P$ is the same for all solvents at the same mole fraction of solute.
3. CThe relative lowering depends only on the number of solute particles per unit amount of solvent, not on the identity of the solute.
4. DDoubling the molality of the solute approximately doubles the relative lowering.