JEE · NEET Previous Year Question

Identify $A$ and $B$ respectively in the following reactions:
$4\text{Au}\text{(}s\text{)}+8{\text{CN}}^{-}\text{(}\text{aq}\text{)}+2H_{2}O\text{(}\text{aq}\text{)}$
$\to O2\text{(}g\text{)}A\text{(}\text{aq}\text{)}+4{\text{OH}}^{-}\text{(}\text{aq}\text{)}\to \text{Zn}\text{(}s\text{)}B+2\text{Au}\text{(}s\text{)}$

Topic: JEE PYQ

Answer: A. Full step-by-step solution below.