NaH is an ionic compound and is made of sodium cations (Na+) and hydride anions (H−). It has the octahedral crystal structure with each sodium ion surrounded by six hydride ions.
CH4 forms molecular or covalent hydrides. These are mainly formed by p - block elements and some s - block elements.
The third compound has an oxidation number of hydrogen which is zero. So it belongs to Interstitial hydride.
In B2H6 the Boron atom is surrounded by 6 electrons, so it is electron deficient due to its incomplete octet.
The correct option is D.