(A) : If blood cells are placed in pure water, they swell and burst.

(R) : Due to osmosis, the movement of water molecules into the cell dilutes the salt content.

Water moves across a membrane through osmosis. Osmosis is started by salt, which attracts water and makes it move toward it and across the membrane. Solutes include salt. When water is added to a solute, it diffuses, dispersing the salt concentration and forming a solution.

Therefore the correct option is (A) Both (A) and (R) are true and (R) is the correct explanation of (A)