Which one of the following properties has the same value for $H_2$ and $D_2$?

Which is the lightest gas?

Hydrogen generally forms covalent compounds. Give reason.

The hydrides of which group elements of the periodic table form electron-precise hydrides?

Identify the correct statements about the hydrides.
$(I)$ In saline hydrides,the oxidation state of hydrogen is $-1$.
$(II)$ $LaH_{2.87}$ is an example of an interstitial hydride.
$(III)$ $NH_3$ and $H_2O$ have the tendency to form hydrogen bonds.
$(IV)$ Electrolysis of molten sodium hydride liberates $H_2$ gas at the anode.

Match List-$I$ with List-$II$

List-$I$ Type of Hydride	List-$II$ Example
$A$. Electron deficient hydride	$I$. $MgH_2$
$B$. Electron rich hydride	$II$. $HF$
$C$. Electron precise hydride	$III$. $B_2H_6$
$D$. Saline hydride	$IV$. $CH_4$

Choose the correct answer from the options given below: