分别通读下面两篇短文，根据短文内容，从A、B、C 三个选项中选出可以填入空白处的最佳答案。

    When I was in high school, I didn't do well in my schoolwork at first.1 I wanted to go to college. I went to talk with my favorite teacher. He told 2 that there might be no chance for me to go to college. It made me very 3 .

    But I didn't give up (放弃). I might not be able to get into 4 . But I wouldn't stop 5 . Then I found that my 6 in the past was spending too much time on science. I was not good at my schoolwork, because I wasn't working hard on all 7 .

    So during the following semesters I 8 my plan. I spent more time in studying English, math and other subjects. I worked hard by 9 to the teachers carefully in class and doing more exercises after class. Now I am studying at college.

    If you are not doing well at school at the moment, don't 10 . Forget the past years and restart (重新开始) now! I believe all your dreams can come true.

将20只生长发育状态相似的蝌蚪，平均分成A、B两组。A组饲喂少量甲状腺激素，蝌蚪的个体发育变化迅速，在比较短的时间内就变成了一群小型青蛙，而不饲喂甲状腺激素的B组蝌蚪则按常规发育。