With which of the following does hydrogen combine directly?

Deuterium resembles hydrogen in properties but:

Consider the following statements:
$1.$ Atomic hydrogen is obtained by passing hydrogen through an electric arc.
$2.$ Hydrogen gas will not reduce heated aluminium oxide.
$3.$ Finely divided palladium adsorbs large volume of hydrogen gas.
$4.$ Pure nascent hydrogen is best obtained by reacting $Na$ with $C_2H_5OH$.
Which of the above statements is/are correct?

Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?

During the electrolysis of fused calcium hydride $(CaH_2)$,where is hydrogen produced?

Consider the following statements and identify which of them are correct:
$I.$ Atomic hydrogen is obtained by applying an electric arc to hydrogen gas.
$II.$ Hydrogen gas does not reduce heated aluminum.
$III.$ Finely divided palladium absorbs a large volume of hydrogen gas.
$IV.$ The reaction of $Na$ with $C_2H_5OH$ yields pure nascent hydrogen.