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!

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    There was once a spider that lived in a cornfield. She liked this home and planned to stay there for the rest of her life.

    One day, the spider caught a little bug (小昆虫) in her web. Just as the spider wanted to eat him, the bug said: "If you let me go, I will tell you something important that can save your life."

    The spider thought for a little while and listened. "You'd better get out of this cornfield," the little bug said. "The harvest (收获季节) is coming!"

    "I think you are just telling me a story," the spider said with a smile.

    "Oh no, it is true," the little bug said." All the stalks (秆) will be knocked down, and the corn will be. You will be killed by the large machines if you stay here."

    "I don't believe you," the spider said as she ate the little bug for lunch.

    A few days later, the spider was laughing about the story the little bug had told her. She thought to herself: "A harvest! What a silly idea. I have lived here all of my life, and nothing has ever troubled me."

    The next day was a beautiful sunny day. The sky above was clear, and there was no wind at all. That afternoon, when the spider about to have a rest, she noticed something like clouds moving toward her. She could hear the noise of a great engine, and she said to herself: "I wonder what that could be?"

    Devike was walking home from school. Everything was bad at school. In the morning, she got to school late. In the math test, half her answers were not right and she forgot to do her English homework. The teacher wrote a message in her notebook for her parents to sign.

    She knew her parents would be angry with her. She also knew she had a lot of schoolwork to do. Just thinking about these, she was sad.

    After she got home, her mother gave her a hug(拥抱) and said, "How was your day, dear?" Her little brother Rohit came to her and said," Hi, sister! I miss you.

    Quickly Devika felt better. Of course, her mom would be angry with her poor grades. But she loves her and that is more important. And her little brother always thinks she is smart and beautiful.

    At that time, Devika felt lucky to have such a great family and she didn't worry about her poor grades because the family could comfort(安慰) her when she was sad.

    It's 21:00 in Beijing now. Let's look at what the four students are doing.