Which is used as Hydrogen generators
A. NaH
B. HI
C. S₆H₃
D. None of these

Hint: To produce hydrogenation we need a compound that is a good reducing agent & which contains hydrogen. Generally, most of the hydrogen-producing compounds are hydrides and mostly the hydrides are good reducing agents. Reducing agents are those chemical compounds that donate an electron and get oxidised to reduce the other chemical compound.

Complete Step by Step Answer:
To chemically produce H₂ gas we need a strong reducing agent and hydrides are strong reducing agents and they produce hydrogen gas in a large amount. Mostly metal hydrides and alkali metal hydrides are used for reduction processes which include the production of hydrogen gas; like Calcium Hydride ($CaH_2$), Lithium Aluminum Hydride ($LiAlH_4$), Sodium Borohydride ($NaBH_2$), etc. Hydrogen is mostly generated/produced from fossil fuels; they are the major source of hydrogen gas. Hydrogen gas can also be produced with the help of the electrolysis of water.

So we can see that; metal hydrides are used for the generation of hydrogen now; NaH (sodium hydride) also produces hydrogen gas when it reacts with water ($H_2O$).
The following reaction is-
$2NaH \ +\ 2H_2O \rightarrow\ 2NaOH \ +\ 2H_{2}$

But $HI$ & $S_6H_3$ does not produce $H_2$ gas. But HI gives $H^+$ ions in the reaction and it is used for the iodination of chemical compounds.
Thus, Option (A) is correct

Note: In many chemical and industrial processes, Hydrogen gas is required. Hydrogen gas is a source of a large amount of energy so it is energy efficient. Hydrogen gas is a clean fuel with no carbon residue. Instruments and machines running on hydrogen fuel run for a longer duration of time