Which pair does not show hydrogen isotopes?

Which of the following statement$(s)$ is/are correct:
$A$. $NaH$ is a non-volatile hydride
$B$. $MgH_2$ is a polymeric hydride
$C$. $NH_3$ is an electron-precise hydride
$D$. $H_2O$ is an electron-rich hydride

Given below are two reactions involved in the commercial production of dihydrogen $(H_2)$. The two reactions are carried out at temperatures $T_1$ and $T_2$ respectively:
$C_{(s)} + H_2O_{(g)} \xrightarrow{T_1} CO_{(g)} + H_{2(g)}$
$CO_{(g)} + H_2O_{(g)} \xrightarrow{T_2} CO_{2(g)} + H_{2(g)}$
The temperatures $T_1$ and $T_2$ are correctly related as:

In the water-gas shift reaction,hydrogen gas is produced from the reaction of steam with

What do you understand by the term "non-stoichiometric hydrides"? Do you expect this type of the hydrides to be formed by alkali metals? Justify your answer.

Which of the following acids does not produce $H_2$ gas upon reaction with alkali metals?