根据材料内容，选择正确答案。

    What was discovered by accident? The answer is penicillin (青霉素). It kills germs. By killing germs, it saves lives. Suppose you are sick. You go to a doctor. She examines you. She says you have a “staph” infection (葡萄球菌感染). She gives you some medicine. You take it. The medicine knocks out the staph. Soon you are well. Before penicillin, this would not happen. Staph was almost sure death.

    Everyone wanted a medicine. Laboratories worked day and night. They grew the staph in small dishes. Then they tried to kill it. Nothing worked.

    The laboratory dishes had covers on them. They kept things from falling into dishes. Molds (霉菌) were a big worry. They are always in the air. You can't see them. They're too small. There are thousands of different molds. Molds can make an experiment (实验) fail. That's why dishes are covered.

    Dr. Alexander Fleming was working to kill the staph germ. He worked for years. One day he took a cover off a dish. He looked inside. There was a thick growth of staph germ. There was also some mold. Then he saw something strange. Where the mold was, there was no growth of staph. This is what Fleming probably thought. “By accident, I found a mold to kill the dreaded staph.”

    This is how penicillin was found. But here's the real miracle (奇迹). There are thousands of kinds of molds. But only one kind can kill staph. The mold must have fallen into the dish a few days before. The cover was probably off only a few seconds (秒). In those few seconds the right mold fell into the right dish. Another man might have thrown the dish away. But Fleming was very careful and smart. He understood what the mold did. How lucky the humans were!

根据短文内容，选择最佳答案

    Once Mr. King had a cat, and he loved it very much. He called it "Sky", because he thought "Sky" was the strongest name in the world.

    One day he had a meal at a restaurant with his cat. He met his old friend. He told him about his lovely cat and its name. His friend said, "How foolish you are! Sky is not the strongest thing in the world. My cat is called „Cloud' because cloud is stronger than sky." After hearing this, Mr. King called his cat "Wind" because he thought wind was stronger than cloud.

    After a few days he suddenly thought that "Wall" was stronger than wind. And "Mouse" was stronger than wall. So he went to his friend to ask for an idea. His friend said, "Don't you think Cat is stronger than mouse？" "Yes, but..."

    The man thought and thought and then decided his cat's name had better be "Cat" because a mouse was always afraid of a cat. Don't you think Mr. King is very silly or funny？

One of the world's most dangerous sports is mountain climbing, and one of the most popular places for this is Himalayas. The Himalayas run along the southwestern part of China. Of all the mountains, Qomolangma rises the highest and is the most famous. It's 8848.86 meters high and so is very dangerous to climb. Thick clouds cover the top and snow can fall very hard. Even more serious difficulties include freezing weather conditions and heavy storms. It's also very hard to take in air as you get near the top.

The first people to reach the top were Tenzing Norgay and Edmund Hillary on May 29, 1953. The first Chinese team did so in 1960, while the first woman to succeed was Junko Tabei from Japan in 1975. 

Why do so many climbers risk their lives? One of the main reasons is that people want to challenge themselves in the face of difficulties. The spirit of these climbers shows us that we should never give up trying to achieve our dreams. It also shows that human can sometimes be stronger than the forces of nature. 

TikTok (抖音) is a video-sharing app that has taken the world by storm. You'll see dancing, jokes and amazing shows. Many people have found great joy in using the app. They feel relaxed when they watch the videos on TikTok after a day's hard work. However, others think it is not a good idea to use it. Some people, especially the young, have been addicted to (沉迷于) the app. They spend too much time on it. This makes them spend less time on their study or work. What's more, it is bad for their health as well. To solve this problem, TikTok has made lots of changes which are designed to protect its teenage users.

"Users aged 13—15 will not get push notifications (推送) from 21: 00, and for 16 to 17-year-olds, from 22:00. This will help them have more time on work, study, relaxation and sleep," the video-sharing app says. TikTok also made some changes that 16 to 17-year-old users will only receive messages which are good for them. "We want our users, especially younger users to develop good habits when using the Internet earlier," TikTok said.

Another change made earlier from TikTok was stricter. It was said that messages could be sent to users over 16s only. As for users aged 16 —17, if they want to send a message to others, they will need to change to a different sharing option (选择), which protects them from bad information. Besides that, before they share their first TikTok, users under 16 will be asked to choose with whom they want to share their videos.

The head of online child safety at the National Society for the the Prevention of Cruelty to Children, Andy Burrows, welcomed the new changes, saying the changes from TikTok would protect teenagers. "I think this will reduce opportunities for offenders (犯罪者) to trick children." Andy said.

Nearly everybody loves oranges. They are sweet and juicy and it is easy to eat them. Some people also like their colour. 

The orange tree is beautiful. It has a lot of shiny(闪亮的) green leaves. Its small white flowers smell very sweet. An orange tree has flowers and fruit at the same time. 

Farmers in other parts of Asia and the Middle East(中东) learned to plant orange trees from Chinese. Then they taught Europeans how to plant orange trees. Later, Europeans took oranges to America. 

In English, "orange" means both a fruit and a colour. We use the name of the fruit for the colour.