To determine which organic compounds polymerize to form the polyester Dacron, we need to understand the chemical structure of Dacron.$\\$Dacron is a type of polyester, specifically polyethylene terephthalate (PET).$\\$It is formed by the polymerization of two monomers: terephthalic acid and ethylene glycol.$\\$Let's analyze the options:$\\$Option 1: Propylene and $para-HO-(C_6H_4)-OH \\$• Propylene is an alkene, and $para-HO-(C_6H_4)-OH$ is a dihydroxybenzene.$\\$• This combination does not form a polyester like Dacron.$\\$Option 2: Benzoic acid and ethanol$\\$• Benzoic acid is a monocarboxylic acid, and ethanol is a monohydric alcohol.$\\$• This combination forms an ester, but not a polyester.$\\$Option 3: Terephthalic acid and ethylene glycol$\\$• Terephthalic acid is a dicarboxylic acid, and ethylene glycol is a diol.$\\$• This combination forms polyethylene terephthalate (PET), which is Dacron.$\\$Option 4: Benzoic acid and $para-HO-(C_6H_4)-OH \\$• Benzoic acid is a monocarboxylic acid, and $para-HO-(C_6H_4)-OH$ is a dihydroxybenzene.$\\$• This combination does not form a polyester like Dacron.$\\$Therefore, the correct option is Option 3: Terephthalic acid and ethylene glycol.$\\$This combination polymerizes to form the polyester Dacron.