Identify the correct acid and conjugate base pair in this equation: hno2 + hs - --> no2- + h2s

Acid: HNO₂

Conjugate base: NO₂⁻

Base:  HS⁻

Conjugate acid:  H₂S

Explanation:

HNO₂ + HS⁻  →   NO₂⁻ + H₂S

This is the reaction of nitrous acid with hydrosulfide, to generate nitrite and  sulfide acid.

HNO₂ is a weak acid that release the proton to the HS⁻, so the HS⁻ is the base.

Proton that is caught by the HS⁻, produce the H₂S so, if the HS⁻ is the base (accepts a proton from other compound), the H₂S acts like the conjugate acid.

In nitrous acid, which is behaving as an acid (a weak one), the nitrite becomes in the conjugate strong base.

i'm assuming that the correct answer is indeed the first one/ "a"..