Which of the following is NOT a consequence of sex separation in the classroom?

Which of the following is NOT a consequence of sex separation in the classroom?
 
  A) Working in same-sex groups becomes more comfortable than mixed-sex groups, which can be problematic later in life for both men and women.
  B) It prevents children from working cooperatively and denies them valuable opportunities to learn from the opposite sex.
  C) Children of both sexes concentrate more fully on the tasks in front of them and less on things such as appearance or excellence in sports.
  D) It reinforces gender stereotypes.

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According to studies of boys and girls in secondary schools
 
  A) physical attractiveness contributes most to the popularity of girls.
  B) athletic achievement contributes most to the popularity of boys.
  C) sexual aggression contributes most to the popularity of girls.
  D) all of the above
  E) both A and B are correct