At the lowest molar concentration at ambient conditions which among the following surfactant will form micelles in aqueous solution ?

Question

$(a)\;CH_{3}(CH_{2})_{15}N^{+}CH_{3}Br^{-}\qquad(b)\;CH_{3}(CH_{2})_{11} OSO_{3}^{-}Na^{+}\qquad(c)\;CH_{3}(CH_{2})_{6}COO^{-}Na^{+}\qquad(d)\;CH_{3}(CH_{2})_{11}N^{+}(CH_{3})_{3}Br^{-}$