Answer is 'Water went into the cell because the concentration of water inside the cell was lower than the concentration outside the cell.'
Osmosis is the diffusion of water molecules, across a semipermeable membrane, from an area of higher water concentration to an area of lower water concentration.
When a cell's cytoplasm has a lower concentration of water than the outer medium of the cell, then water will enter the cell through osmosis. It is mainly due to osmotic imbalance that excessive water molecules get into the cell, causing it to swell and eventually burst.
It is ideally an animal cell that bursts due to osmosis because they lack the cell wall which may prevent it from bursting.
