Why does `H^(+)` ion always get associated with atoms or molecules ?

Options

A. lonisation enthalpy of hydrogen resembles that of alkali metals.
B. Its reactivity is similar to halogens
C. It is resembles both alkali metals and halogens.
D. Loss of an electon from hydrogen atoms results in an nucleus of very small size as compared, to other atoms or ions. Due to small size it cannot exist free.

Explanation

(d) is the correct answer