Answer: Hydrogen bond.
Explanation: Water is a polar covalent molecule in which two hydrogen atoms are bonded to central oxygen atom via single covalent bonds. So, metallic, nonpolar covalent or ionic choices are not correct. The only correct choice is hydrogen.
Hydrogen bonding is present in ice as we know that hydrogen bonding takes place when hydrogen is bonded to the more electron negative atoms(F, O or N). Density of ice decreases as the molecules are farther from each other due to the presence of hydrogen bonding. This hydrogen bonding breaks when ice melts to water and the molecules comes closer.