Density of ice is less than that of water because of:

The correct option is C open porous structure of ice due to hydrogen bonding

Ice is less denser than water because in ice, the molecules arrange themselves in a rigid tetrahedral structure due to which cage like spaces remain in their bonding but water molecules remain in linear bonding form. As the volume of ice becomes greater, it is less denser. Density of ice is less than that of water because of open porous structure of ice due to hydrogen bonding.