Zeolite is hydrated sodium aluminium silicate. When treated with hard water,the sodium ions in zeolite are exchanged with

Which of the following is not used for softening of water?

Observe the following statements:
$1.$ Heavy water is harmful for the growth of animals.
$2.$ Heavy water reacts with $Al_4C_3$ and forms $\text{deuterated acetylene}$.
$3.$ $BaCl_2 \cdot 2D_2O$ is an example of $\text{interstitial deuterate}$.
The correct statements are:

How is the oxygen atom surrounded in ice?

Which of the following is heavy water?

Provide general information about water $(H_2O)$.