Two moles of aluminum chloride are dissolved in two liters of water.

How does the vapor pressure of the water change?

It does not change because the amount of water in the system remains constant in both systems, and water is the only volatile compound in this system.
It first decreases as aluminum chloride attracts the water molecules, but it then increases as dissolving completes and starts to push water molecules out.
It increases because aluminum and chloride ions displace water molecules, which escape into the gas phase.

It decreases because nonvolatile aluminum and chloride ions now occupy some of the volume of the system.