Hydrogen cyanide, hcn, is a weak acid. which equation best represents its aqueous chemistry?

The equations are as follow,

A)  HCN (aq) + H₂O (l)   ↔  H₂CN⁺ (aq) + OH⁻ (aq)

B)  H₂O (l)    ↔   H⁺ (aq) + OH⁻ (aq)

C)  HCN (aq)   ↔   H⁺ (aq) + CN⁻ (aq)

D)  HCN (aq) + H₂O (l)    ↔     CN⁻ (aq) + H₃O⁺ (aq)

E)  HCN (aq)     ↔    H⁻ (aq) + CN⁺ (aq)

            Option-D is the correct answer.

Explanation:
                    When hydrogen cyanide is added in water it partially ionizes as follow,

                       HCN (aq) + H₂O (l)    ↔     CN⁻ (aq) + H₃O⁺ (aq)

Being weak acid it fails to completely dissociate into H⁺ and CN⁻ ions. In this reaction water is acting as a Bronsted Lowery Base and picks proton from from HCN and converts into conjugate acid (i.e. H₃O⁺), while, HCN converts into conjugate Base (i.e. CN⁻).