问题：
[单选题]An aqueous BSA* solution in the tube on the left is in equilibrium with pure water in the tube on the right. The membrane that separates the two solutions is only permeable to water. When salt is added to the pure water on the right,
A.the water level on the right increases
B.the BSA solution level on the left increases
C.no change in the levels occur
*BSA=Bovine serum albumin protein
