Explanation

(b)
Dodecyl trimethyl ammonium chloride $C_{12}H_{25}\left( CH_{3} \right)_{3}NCl$ on dissolution forms $C_{12}H_{25}\left( {CH}_{3} \right)_{3}N^{+}$ and $Cl^{-}$ ions. The former possesses hydrophilic $( - N^{+})$ and hydrophobic $\lbrack C_{12}H_{25}\left( {CH}_{3} \right)_{3}^{-}\rbrack$ parts.