Two similar animal cells are placed in two different solutions:

• Cell X is placed in pure water.
• Cell Y is placed in a concentrated salt solution.

Cells are observed after some time. Cell X swells, and Cell Y shrinks. Which statement provides the correct explanation for the above observations?

(i) Salt molecules moved into Cell Y, causing it to shrink.

(ii) Water moved into Cell X and more water moved out of Cell Y than the salt solution entered in it.

(iii) Water moved into Cell X and moved out of Cell Y through the cell membrane.

(iv) Solute movement caused osmosis in both cells.

The correct statement is (iii) Water moved into Cell X and moved out of Cell Y through the cell membrane.

Cell X is placed in pure water, which is a dilute (hypotonic) solution. Water moves into the cell by osmosis from a region of higher water concentration (outside) to a region of lower water concentration (inside), so the cell swells. Cell Y is placed in a concentrated salt solution, which is a hypertonic solution. Here, water moves out of the cell by osmosis, so the cell shrinks. The cell membrane is selectively permeable and allows only water, not the salt, to pass through. This is why options involving the movement of salt molecules (i, ii) or solute movement (iv) are incorrect.