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5、According to popular folk tales, many animals are smarter than they appear. Dogs bark before earthquakes; cattle predict rainful by sitting on the ground. But cattle may have another hidden talent of being able to tell which direction is north.

    Small animals__ including birds__ are known to use the Earth’s magnetic （磁場的） fields in migration （遷徙）, like a natural GPS （ Global Position System ）. Dr. Begall and her colleagues wanted to know whether larger animals also have this magnetic sense. They investigated this possibility by studying images of 8,510 grazing （吃草） and resting cattle in 308 plains across the globe on Google Earth, a website that puts together satellite photographs to produce an image of the Earth’s surface.

    Grazing animals are known to orient （使朝向） themselves in a way that minimizes wind cold from the north and maximizes the warmth of the sun when they are cold. The study ruled out the possibility that the sun position or wind direction were major influences on the orientation of the cattle. The researchers therefore had to study a lot of cows grazing in lots of different places at different times of day, in order to average out these factors and see whether cattle could act like compass needles.

    The researchers concluded that cattle do generally orient themselves in a north-south direction. This north-south preference has also been noted in flies and honeybees. But unfortunately, even the high resolution of Google Earth is not powerful enough to tell which end of the cow is its head, and which its tail. The researchers were therefore unable to answer their research questions of whether cattle prefer to look north or south, and whether that differs in the northern and southern hemisphere.（半球）

1. Which of the following factors might affect Dr. Begall’s research result?

    A. Rainful.                B. Earthquakes.           C. Location.                       D. Cost.

2. What is the major finding of Dr. Begall’s study?

    A. Cattle orient themselves along a north-south axis.

    B. Magnetism cannot be studied scientifically.

    C. Animals prefer to look south.

    D. Google Earth is a reliable research tool.

3. Why were the researchers unable to get the answers to their research questions?

    A. Many cattle in their study were sitting on the ground.

    B. The cattle constantly change directions to avoid wind cold.

    C. There is a magnetic difference between the two hemispheres.

    D. They could not tell a cow’s head from its tail in the satellite pictures.