To solve this problem, we need to analyze the given reaction:$\newline$The starting compound is phthalaldehyde, which reacts with $2[Ag(NH_3)_2]^+$ and $3OH^-$ under heat.$\newline$This is a typical reaction for the oxidation of aldehydes using Tollen's reagent.$\newline$Step-by-step mechanism:$\newline$1. The aldehyde group in phthalaldehyde is oxidized by Tollen's reagent.$\newline$• The aldehyde group (CHO) is converted to a carboxylate group (COO^-).$\newline$• Silver ions are reduced to metallic silver, which is not shown in the product.$\newline$2. The major product is the dicarboxylate form of the starting compound.$\newline$Analyzing the options:$\newline$• Option 1: Incorrect, as it shows a diol.$\newline$• Option 2: Incorrect, as it shows a ketone and alcohol.$\newline$• Option 3: Correct, as it shows the dicarboxylate product.$\newline$• Option 4: Incorrect, as it shows a carboxylate and alcohol.$\newline$Therefore, the correct option is Option 3.