How many hydrogen atoms are surrounding each oxygen atom in the structure of ice?

Which of the following is a bad conductor of electricity?

$100 \, mL$ of a water sample contains $0.81 \, g$ of calcium bicarbonate and $0.73 \, g$ of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of $CaCO_3$ is .............. $ppm$ (molar mass of calcium bicarbonate is $162 \, g \, mol^{-1}$ and magnesium bicarbonate is $146 \, g \, mol^{-1}$)

Identify the correct statements from the following.
$A$. In photosynthesis reaction,water is oxidized to oxygen.
$B$. An example for interstitial hydride is $MgH_2$.
$C$. Sodium hexametaphosphate is used in the removal of permanent hardness of water.

Identify the incorrect statement regarding heavy water $(D_2O)$.

Which compound produces $H_2$ gas in an aqueous solution?