Which of the following forms cationic micelles above certain concentration?

Solution :
Cetyltrimethylammonium bromide forms cationic micelles above a certain concentration. In the molecule of detergents and soap, the negative ions aggregate to form a micelle of colloidal size. In polar medium ( like water ), the negative ion has a long hydrocarbon chain and a polar group $$\left( { - CO{O^ - }} \right)$$   at one end and on other end, it has $${N^ + }$$ $$ion,$$  thus cationic micelle is formed.