为了探究菜豆种子萌发所需要的外界条件，某生物兴趣小组选取数粒饱满的菜豆种子，平均分为三组，分别放入三个相同的烧杯中．其中，A烧杯内，菜豆种子下有一块干棉絮； B烧杯内，菜豆种子下有一块湿棉絮；C烧杯内，菜豆种子浸没在煮沸的水中，液面上还有一层食用油．将三个实验装置放在光下培养7天，温度等其他管理条件相同，观察记录实验现象（见如图）．请据题意回答问题。

根据图片完成句子

In 1961 Obama was born in Hawaii, US. His father is an African and his mother is a white American. He grew up in Indonesia and Hawaii.
When Obama was 10 years old, he was one of only three black students at his school in Hawaii. He felt very different from most other students. White girls wanted to touch his hair. A white boy even asked him what his father was.
“I lied to them that my father was a Kenyan prince（王子）. But I kept asking myself who I am,” said Obama.
However, 37 years later, the boy made history. Obama became the first black president（总统） in US history.
This unusual background（背景） made him wonder who he was. He once turned to alcohol (酒) to help forget this question.
With the help of his friends, Obama finally turned his life around at college. His hard work made him a star at Harvard. Later, he became only the third black senator (参议员) in US history.
“Obama’s success has made Martin Luther King’s dream come true. That is: A man should not be judged （判断）by the color of his skin, but by the content of his character,” wrote ABC news.