通读下面短文，掌握其大意，然后在每小题所给的四个选项中，选出一个最佳答案。
At the age of 13, David always played with a group of kids.
Because he was so busy playing, he didn't study enough and1 his final exam.
One morning, when David was about to2 with his friends, his father stopped him and
said calmly, "David, you're spending so3 time playing all day that you failed your
exam. I'm worried about your future."
"What are you worrying about? Jack and Robert also failed,
but don't they still get to go fishing?"
"My boy, you can't think like that," his dad said.
"Let me4 a story."
"There were two5 playing on a roof. Then they fell down the
chimney. When the two cats climbed out of the chimney, one of the cats had
soot(烟灰) on his face, while the other cat's face was6. Seeing the soot-faced
cat, the clean cat thought its face must be dirty, so it7 ran to the riverside and washed its face. The
soot-faced cat saw the clean-faced cat and thought its face was also clean,8 it just ran down the street."
"David, no one can be your '9'. You have to think for
yourself. If you always follow others, you will10 learn."
Hearing this, David returned to his room. He decided to pay more
attention to his studies and less attention to what his friends were doing.
This allowed him to be successful.
