The wall of a cell is semi-permeable. When there is a change in the concentration of salts across the two sides of the cellular wall, water flows from one side to the other in an attempt to equate the concentrations on both the sides.

The concentration of sodium chloride in the cell is 0.09%. If the pressure of sodium chloride were higher outside the cell, water would flow out through the cell wall. This would reduce the size of the cell. On the other hand if the concentration of NaCl were higher inside the cell, water would flow into the cell and its size would thereby increase.

For the given cases, when the cell is placed in a solution with a sodium chloride concentration of 0.0009%, the size of the cell increases. When the cell is placed in a sodium chloride solution with a concentration of 0.9%, water flows of the cell decreasing its size. Similarly in case c, the cell's size increases, the cell's size is constant in the case d and in case e the cell's size decreases.