The composition of water gas is

Which property of hydrogen distinguishes it from alkali metals?

The total number of isotopes of hydrogen and the number of radioactive isotopes among them,respectively,are:

The correct statements among $(a)$ to $(d)$ are:
$(a)$ Saline hydrides produce $H_2$ gas when reacted with $H_2O$.
$(b)$ Reaction of $LiAlH_4$ with $BF_3$ leads to $B_2H_6$.
$(c)$ $PH_3$ and $CH_4$ are electron-rich and electron-precise hydrides,respectively.
$(d)$ $HF$ and $CH_4$ are called as molecular hydrides.

Among the following,the correct statements are:
$I$. $LiH, BeH_2$ and $MgH_2$ are saline hydrides with significant covalent character.
$II$. Saline hydrides are volatile.
$III$. Electron-precise hydrides are Lewis bases.
$IV$. The formula for chromium hydride is $CrH$.
The correct option is:

Explain the laboratory preparation of dihydrogen.