Osmosis has taken place in the said situation.
Option C
An egg is actually a cell covered by its cell membrane and protected by a layer of calcium salts outside it. The calcium salt present in the shell of the egg is actually mostly calcium carbonate.
Calcium carbonate is reactive with vinegar which is basically aqueous solution of acetic acid. The reaction produces calcium acetate and carbon dioxide which evolves out, leaving the cell membrane of the egg.
The egg membrane is semi permeable and the cytoplasm of the egg is very much concentrated with proteins and other enzymes. The outside solution of vinegar is very much dilute with respect to the cytoplasm of the egg. So water enters the cell through cell membrane by endosmosis.