二、阅读短文，根据短文内容，完成下列各题。
〔哲理故事〕Socrates was a great thinker. He had a student called Plato.
One day, Socrates said to his students, “Today you are going to learn a new kind of exercise, swinging arms forward and then backward.” He told his students how to do the exercise. Then he asked his students to swing their arms 300 times every day.
“Do you think you can do it?” Socrates asked the students.
The students said, “Yes, of course. It is not difficult.” So all the students told Socrates that they would do the exercise every day.
A month later, Socrates asked his students, “Which of you do the exercise every day?” Socrates was happy that all the students did it.
Another month went by. He asked the students the same question, but only 80% of the students put up their hands. The exercise became difficult for the students.
“Well, doing one thing is not difficult but doing the same thing every day is difficult. That’s why some people can succeed but some can’t,” Socrates said to his students.
A year later, Socrates asked his students the same question again. This time, only Plato put up his hand. Later he also became a great thinker.
16. What was the new kind of exercise Socrates asked his students to do?

17. Why did all the students promise they would do the exercise every day at the start?

18. How many students did the exercise every day after two months?

19. What can you learn from the story? ( within 15 words )

16.Swinging arms forward and then backward.
17.Because they thought it was not difficult.
18.(Only) 80% of the students.
19.If we want to succeed, we should keep working hard.