Which of the following substance$(s)$ is/are used in the laboratory for drying purposes?

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:

Which of the following substances can be used for drying gases?

In $para-hydrogen$,what is the nature of the electron spin?

What do you expect the nature of hydrides is,if formed by elements of atomic numbers $15$,$19$,$23$,and $44$ with dihydrogen? Compare their behaviour towards water.

Which of the following will not be reduced by $H_2$?