Hint: We have to remember that the critical micelle concentration can be called as the concentration of surfactants at which micelles formed. As soon as CMC reaches, surface tension becomes constant or becomes relatively lower. And before CMC, it is strongly equal to concentration of surfactants. Micelle can be formed by aggregating the molecules together.
Complete answer: We must look at all the options before answering. We need to remember that the micelles are nothing but the aggregation of surfactant molecules at critical micelle concentration. Option A) this option can be correct as the surfactant molecule associates to form micelle at critical micelle concentration but we will look at all the options given. Option B) This option can be correct as the surfactant molecules aggregate together to form micelle at CMC, but we must look at all the options given. Option C) this option can be correct as the surfactant molecules will lead to the formation of micelles when the surfactant molecules aggregate together they form a micelle at critical micelle concentration. Option D) this is a correct option as all of the above options given are correct.
Note: For the formation of micelle, it is formed by the aggregation of surfactant molecules. The molecules associate together to form micelle and this process takes place above critical micelle concentration. We must have to remember that the micelles contain both hydrophobic and hydrophilic parts out of the long chain and polar head, the former is hydrophobic while the other is hydrophilic in nature.