The method used to remove temporary hardness of water is

What is $X$ in the following reaction?
$MgCl_2 + 2H_2O \to X + 2HCl + H_2O$

Provide general information about water $(H_2O)$.

Which of the following compounds is used for the softening of hard water by Clark's method?

Which of the following is heavy 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: