To solve this problem, we need to identify the compounds $A, X, Y,$ and $Z$ in the given reaction sequence.$\newline$Let's analyze the reactions step-by-step:$\newline$1. The first reaction involves $X$ (C$_2H_6O)$ reacting with copper at 573 K to form $A. \newline$• $X$ is ethanol (C$_2H_5OH). \newline$• Ethanol is oxidized to ethanal (acetaldehyde, CH$_3CHO)$ in the presence of copper.$\newline$• Therefore, $A$ is ethanal.$\newline$2. The reaction of $A$ with $[Ag(NH_3)_2]^+$ results in a silver mirror.$\newline$• This indicates the presence of an aldehyde, confirming that $A$ is ethanal.$\newline$3. The reaction of $A$ with $-OH$ and heat leads to the formation of $Y. \newline$• This is an aldol condensation reaction.$\newline$• Ethanal undergoes aldol condensation to form but-2-enal (crotonaldehyde).$\newline$• Therefore, $Y$ is but-2-enal.$\newline$4. The reaction of $A$ with semicarbazide forms $Z. \newline$• Ethanal reacts with semicarbazide to form a semicarbazone.$\newline$• Therefore, $Z$ is the semicarbazone of ethanal.$\newline$Analyzing the options:$\newline$• Option 1: Incorrect compounds.$\newline$• Option 2: Correct compounds (A-Ethanal, X-Ethanol, Y-But-2-enal, Z-Semicarbazone).$\newline$• Option 3: Incorrect compounds.$\newline$• Option 4: Incorrect compounds.$\newline$Therefore, the correct option is Option 2.