What is $X$ in the following reaction?
$NaH + B_2H_6 \xrightarrow{\text{Diethyl ether}} X$

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

List-$I$ (Hydrides)	List-$II$ (Nature)
$a. MgH_2$	$i. \text{Electron precise}$
$b. GeH_4$	$ii. \text{Electron deficient}$
$c. B_2H_6$	$iii. \text{Electron rich}$
$d. HF$	$iv. \text{Ionic}$

Choose the correct answer from the options given below:

Identify the correct statements from the following:
$(I)$ The formula of Calgon is $Na_6(PO_3)_6$.
$(II)$ Exhausted permutit is regenerated by aqueous $KCl$ solution.
$(III)$ Calcium stearate is soluble in water.
$(IV)$ In ice crystals,each oxygen is surrounded by four oxygen atoms.

Ortho- and para-hydrogens have

The gas used in the hydrogenation of oils in the presence of nickel as a catalyst is

An alkali metal hydride $(NaH)$ reacts with diborane in '$A$' to give a tetrahedral compound '$B$' which is extensively used as a reducing agent in organic synthesis. The compounds '$A$' and '$B$' respectively are