Today there are many fires than in the past. Over 100,000 wildfires burn each year in America. Russia has 20,000 to 35,000 wildfires every year. Australia has on average 60,000 each year. These fires destroy（损害）huge areas of forests and burn hundreds of homes.

Many experts believe there are several reasons for this sudden increase in fires. The first reason is climate（气候）change. Recent weather has been warmer and drier. This leads to dangerous fire conditions. When lightening strikes（发生雷电），dry grass easily catches fire. Hot winds add to the problem. The wind spreads a fire quickly. In 2010, Russia had the hottest and driest summer in a century. In just one month, 500 fires destroyed over 2,000 homes. Some people lost their lives.

Traditional fire-fighting practices are another reason for the increase in fires. In America, firefighters used to quickly put out every fire. They didn't allow the grass and trees to burn. As a result, today many forests have thicker vegetation（植被）.Thicker vegetation means more fuel（燃料）for fires. Also, without fires from time to time, forests become overcrowded and unhealthy. Some trees are dead. The dead wood then easily catches fire. So surprisingly, America has many more fires today partly because of its past fire-fighting practices.

Scientists now understand that a fire can be a natural part of a healthy forest. As a result, countries like Australia allow more fires to burn naturally. Sometimes, fire fighters even start fires to get rid of（去除）dead wood. Of course, they carefully control the fires. The fire thins out old trees. This allows sunlight to reach the ground. As a result, fires help new trees to grow. Therefore, if a fire is not a serious threat（威胁）to people, firefighters may let it burn naturally.

    Anyone who has had a long-term illness knows that recovering at home can be lonely. This is can be especially true of children. They may feel isolated（孤立的）from their friends and classmates. Now, a small robot may help children who are recovering from a long-term illness in the hospital or at home. The robot takes their place at school. Through the robot, the children can hear their teachers and friends. They can also take part in classroom activities from wherever they are recovering – whether at home or from a hospital bed.

    The robot is called AV1.It is created by a company called “No Isolation”. AV1 goes to school for a child who is at home while recovering from a long-term illness. And the child's school friends must help. They carry the robot between classes and place the robot on the child's desk.

    Dolva, one co-funder （创始人）of No Isolation, explains how the robot AV1 works. She says, “the robot sits at the child's desk in the classroom and the child at home uses a tablet（平板电脑）or a phone to start it, control its movement with touch, and talk through it. So the robot becomes the eyes, the ears and the voice of the child at school.” The robot is equipped with speakers, microphones and cameras that make communicating easy. Moreover，The AVI was designed to be tough. It is water-resistant(防水) and can take a fall from a desk without damage. Inside AV1 is a small computer connected to a 4G network. AV1 is large and looks like a human for a reason. Dolva thinks this is important because the robot is expected to be a friend to the children.

    The robot just became available to the public. Hopefully AV1 will help some children feel less lonely while they are absent from class.

    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 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. 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. 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!

    Dragon Boat Festival is a fun Chinese holiday. Usually, it's in June or July. Both children and adults（大人）like this holiday.

First, there are dragon boat races. Dragon boats are very long. They have bright colours, In each boat, there are many people rowing（划）. There's also somebody beating a drum（击鼓）. The winners（获胜者）of the races can get a lot of money.

During Dragon Boat Festival, people also eat a special kind of food-rice dumplings. To make these dumplings, people prepare（准备）many things. Then they can make different flavors of dumplings. Some are sweet（甜的），some are salty（咸的）. They all taste good. People give them to friends.

On the evening of the holiday, families have a big meal together. Dragon Boat Festival is a great time for everybody.