Which of the following reactions produces hydrogen?

Ordinary hydrogen at room temperature is a mixture of

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: Loss of electron from hydrogen atom results in a nucleus of $\sim 1.5 \times 10^{-3} \ pm$ size.
Reason $(R)$: Proton $(H^+)$ always exists in combined form.
In the light of the above statements,choose the most appropriate answer from the options given below:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$ : Hydrogen is the most abundant element in the Universe,but it is not the most abundant gas in the troposphere.
Reason $R$ : Hydrogen is the lightest element.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following elements forms a covalent electron-deficient hydride?

In which of the following processes is the highest purity $(99.9 \%)$ hydrogen obtained?