The writer finds it necessary to join a study group

because …

are clever than them
Study groups are commonly utilized by many students to prepare themselves for class discussions, examinations or class presentations. They can also make use of it to review their weak points and learn new ideas. I myself find that we can learn more effectively in a study group. How ever, I can’t deny that study groups have also some disadvantages.
  Which of the following is not suitable to complete the dialogue above?