Which among the following is the strongest acid?

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R:$
Assertion $A :$ The amphoteric nature of water is explained by using Lewis acid/base concept.
Reason $R :$ Water acts as an acid with $NH_{3}$ and as a base with $H_{2}S$.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following is both basic and a reducing agent?

Explain the Bronsted-Lowry theory for acids and bases.

Which of the following is a Lewis base?

When hydrogen chloride is dissolved in acetic acid,the following equilibrium is established: $HCl + CH_3COOH \rightleftharpoons Cl^- + CH_3COOH_2^+$. Identify the conjugate acid-base pairs.