Option C - osmosis is the right answer.
Osmosis is the biological process whereby water moves from a place of high concentration to a place of low concentration through a semi permeable membrane. If a lot of water moves into the cell it is possible for the cell to burst.
Active transport is the biological process whereby ions and molecules cross a cell membrane with the use of energy.
Enzyme activity and respiration (act of breathing) are not related to the movement of water, ions or molecules across a cell membrane.