Nenjamin Franklin(1706-1790)

Benjamin Franklin was an American writer, printer, scientist and inventor. He helped found America and also invented many useful things. But Franklin's first invention was just for fun. As a kid, Ben loved swimming. He wanted to go faster. So he made the early swim fins(脚蹼) to help him.

21. Which of the following was created by chance?

A. The earmuffs. B. The Popsicle.

C. The early swim fins. D. The safety design for looms.

22. What can we learn about Chester Greenwood's first earmuffs?

A. They were just for fun. B. They were part of a hat.

C They were made by his grandmother. D. They were given to his mother as a gift.

23. Whose invention was designed to help others?

A. Frank Epperson's B. Margaret Knight's

C. Benjamin Franklin's D. Chester Greenwood's.

B

In 2016, the news was full of stories about dangerous drinking water in Flint, Michigan. The water had too much lead(铅）in it. Gitanjali Rao, 11, could not stop thinking about how worrying it must be to have polluted water coming out of your water tap.

There were home test machines that could detect(发现)lead in water. But these tests didn't work very well. They took too long and often gave wrong results. Gitanjali wondered if she could create a test that was quick, easy and right.

One day, Gitanjali read a news story about using carbon nanotubes(碳纳米管) to test for harmful things in the air. She wondered if she could use the same idea to detect lead in water.

To test her idea, Gitanjali needed a safe lab with tools that could sense tiny amounts(数量) of lead. She wrote to many labs with her idea, and every time she heard the same thing:"We can't let an 11-year-old kid in here." Or they didn't reply at all. Was her ideas so bad? What was she doing wrong?

Finally, Giranjali decided she was asking the wrong people. She emailed a chemistry teacher at her school. They didn't have a big lab, but it was good enough for Gitanjali to test whether her detector could sense lead at all. She had been paying too much attention to the equipment at big labs. But maybe she didn't need it just to show her basic idea worked.

After many, many tries---her detector worked. Then Gitanjali made a phone app so users could see the results at once on their phones. She entered her idea in a big national competition in 2017 and later was named "America's Top Young Scientist".

24. What did Gitanjali learn about Flint in 2016?

A. The people there spread news quickly.

B. The air pollution there was getting worse.

C. The drinking water there was unsafe to drink.

D. The water there was turned off several times a day.

25.What was the problem of those old home test machines?

A. They took up too much space. B. They couldn't be carried easily.

C. They did harm to people's health. D. They couldn't always get good