A、Girls themselves. B、Governments. C、Mass media. D、Policy makers. C由原文可知，人们怀疑模式化思想的出现是受媒体、老师、家长或其他孩子的影响。因此答案为C。

The study on 400 children, in the journal Science, initially found both five-year-old boys and girls thought their own gender was "brilliant. " But then only one year later, gender differences had emerged.
    The team from Princeton University, New York University and the University of Illinois said it appeared that stereotypes were starting to show. Suspected influences include exposure to media, teachers, parents and other children.
    The study put sets of five-, six- and seven-year-olds through different experiments.
    In one, the children were read a story about someone who is "really, really smart" but it is not clear who the story is about. They then had to guess the character from four pictures—two of men and two of women.
    At age five, boys pick men and girls pick women around 75％ of the time. But fast-forward a year to age six, boys are still picking men while girls are now slightly more likely to pick men too.
    In another scenario, groups of children played a new board game.
    But for some it was branded as "for children who are really, really smart" and for others it was described as " for children who try really, really hard. "
    Six- and seven-year-old girls were as likely as boys to enjoy the game for those who try, but much less likely to say they enjoy the game for smart children.
    Prof. Andrei Cimpian, one of the researchers, told the BBC News website: " The message that comes out of these data is that young kids are exposed to the cultural notion that genius is more likely a male than a female quality. "
    Questions 9 to 11 are based on the passage you have just heard.
    9. When do boys and girls feel gender differences?
    10. Where do stereotypes might come from?
    11. What kind of cultural notion are young kids exposed to according to Prof. Andrei Cimpian?