In many high schools, there are strict rules about using mobile phones. If your phone rings in class, for example, the teacher will be very angry.

    Every mobile phone has a ringtone (铃声). It tells you that someone is calling you. Now, there is a ringtone called "mosquitotone (蚊子铃声)". Using it, students can receive calls and text messages (短信) in class but the teacher will not realize what is happening. How?

    Mosquitotone has a special sound. Only children and teenagers can hear it. As we get older, we are unable to hear some sounds with high frequencies (频率). As a result, a child or teenager can hear the mosquitotone ringtone, but someone of 20 or older can't.

    But sometimes, people over 20 can hear the ringtone. One British student's phone uses mosquitotone. In class, the student's phone rang. The 22-year-old teacher looked at the student and became unhappy. "I heard that. You know the rule: no mobile phone in class."

    Not all the students are interested in mosquitotone. Jerry Jones, a high school student of 17, says, "Using mosquitotone too often is bad for our hearing. I may use it for pleasure, but not in class. It's unfair(不公平的) to the teachers!"

    What do parents think of mosquitotone? "I think it is perfect for places like movie theaters," says Connie Neeson, 44. "Think about it. You're watching a film and someone's mobile phone rings. Mosquitotone is good because many people don't hear it. However, it also has a bad influence（影响） on their study if students use it in class."

    Have you ever had the strange feeling that you were being watched? You tum around and, sure enough, someone was looking right at you!

Parapsychologists(R y3)say that humans have a natural ability to sense when someone is looking at them. To research whether such a "six sense" really exists, Robert Baker, a psychologist(心理学家) at the University of Kentucky, did two experiments.

    In the first one, Baker sat behind unknowing people in public places and stared at the backs of their heads for 5 to 15 minutes. The subjects(受试者)were eating, drinking, reading, studying, watching TV, or working at a computer. Baker made sure that the people could not tell that he was sitting behind them during those periods. Later when he questioned the subjects, almost all them said they had no sense that someone was staring at them.

    For the second experiment, Baker told the subjects that they would be stared at from time to time from behind in a laboratory setting. The people had to write down when they felt they being stared at and when they weren't. Baker found the subjects were no better at telling when they were stared at and when they weren't.

    Baker concludes that people do not have the ability to sense when they are being stared at. If people doubt the outcome of his two experiments, said Baker," I suggest they repeat the experiments and see for themselves

    Populations of white-tailed deer(白尾鹿) are growing rapidly in many parts of the United States. As populations grow, food becomes a problem. Many deer die of hunger. Others grow up small and unhealthy. In search of food, hungry deer move closer to where humans live. They eat farm crops, vegetables and even trees. Besides, increased numbers of deer near roads can cause traffic accidents.

    People admire the grace and fast speed of deer. Most people don't want these animals to be hungry and ill. Should people take action to control the growing deer populations?

Should People Take Direct Action?

    Many people think that hunting(打猎) is the best way to control the animal populations. Wildlife managers will see if there's enough food in an area and decide its carrying capacity(容量). Then hunters with licenses are sent to help control the number of deer. Hunting is usually not allowed in cities or suburbs, however.

    Some people have the idea to catch the deer and move them to other places. But this method is expensive and requires finding another place that can accept the deer without breaking the balance of ecosystem(生态系统).

    Scientists are also working to develop chemicals(化学药品) to control the birth rate(率) in deer populations. But this plan works for only one year at a time.

Should People Take Indirect Action?

    Some suggest bringing in natural enemies of deer, such as wolves, lions and bears, to areas with too many deer. But these animals could also hurt dogs, cats, and even humans. Other communities have built tall fences(篱笆) around areas to keep out the deer. However, this is impossible for farmers.

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    Some people are against any kind of action. They support leaving the deer alone. Animal populations in an area naturally go up and down over time. Doing nothing means that some deer will die of hunger or illness. But finally, the population will reach a size within the carrying capacity(容量) of the environment. So, let nature go its own way.

Word box: location 地点

    Many people have the wrong ideas about pigs. Pigs are actually(买际上) very clean animals. On farms, they live in dirty places, so they become very dirty. But in the wild, pigs keep themselves very clean.

    They are also very smart. They may he smarter than clogs. So pigs can learn things from people.

    Pigs are very friendly animals. Some people raise (饲养) them as pets. Of course, people raise the smart kind, not the big kind. Small pigs are very cute. And they don't break things in the house. Big pigs usually live outside on the farms, not in people's houses.