To solve this problem, we need to identify which of the given options is a cationic detergent.$\newline$Detergents are classified based on the nature of the charge on the hydrophilic part of the molecule.$\newline$• Cationic detergents have a positive charge on their hydrophilic part.$\newline$Let's analyze each option:$\newline$Option 1: Sodium stearate$\newline$• Sodium stearate is an anionic detergent because it contains a negatively charged carboxylate ion.$\newline$Option 2: Cetyltrimethyl ammonium bromide$\newline$• Cetyltrimethyl ammonium bromide is a cationic detergent.$\newline$• It contains a positively charged ammonium ion $(N^+). \newline$Option 3: Sodium dodecylbenzene sulphonate$\newline$• Sodium dodecylbenzene sulphonate is an anionic detergent due to the negatively charged sulphonate group.$\newline$Option 4: Sodium lauryl sulphate$\newline$• Sodium lauryl sulphate is also an anionic detergent because of the negatively charged sulphate group.$\newline$Therefore, the correct option is Option 2: Cetyltrimethyl ammonium bromide, which is a cationic detergent.