三、阅读表达。
阅读下面短文，按要求完成19～23题。
Some students from Shenzhen found that it was not safe for workers to clean manhole covers（排水井盖）on rainy days. So they wanted to do something to help. They built a team and planned to make a machine. With the machine, the workers can work safely.
After long hard work and many experiments, these students made such a machine. They called it Xun’an. “It was hard to make it and we met many difficulties,” said Xiao, the head of the team. “To solve them, we kept on searching for information, working with our team-mates and getting help from our teachers.” Every member did his or her best to help. Three months later, they succeeded（成功）in making this machine.
19、20题完成句子；21～23题简略回答问题。
19. It was for workers to clean manhole covers when it was rainy.
20. To help workers, the students built a team and planned to make a .
21. What’s the name of the machine made by the students?

22. How did the students solve difficulties they met when making the machine?

23. How long did the students spent on this machine?

19. not safe
20. machine
21. Xun'an.
22. They kept on searching for information, working with their teammates and getting help from their teachers.
23. Three months.