Which one of the following statements is correct?

1. (a)The boiling point of an aqueous solution is higher than that of pure water
2. (b)Addition of solutes to a solution causes an increase in its water potential
3. (c)The vapour pressure of the water in a solution is lower than that of pure water
4. (d)When a solution is separated from water by a semi permeable membrane, water movement can be prevented by applying pressure to the solution