阅读理解。 In the summer of 1978 an English

问题：

阅读理解。

     In the summer of 1978 an English man named Steven was driving his tractor through a field of wheat

when he discovered something strange. Some of his wheat was lying on the ground. The flattened wheat

formed (形成) a circle about six meters across. Around this circle were four smaller circles of flattened wheat.

     Three years later a farmer who lived nearby discovered almost the same circles in one of his fields. These

circles were larger-nearly 15 meters across. That same year, another English farmer discovered three circles

of flattened wheat on his land-one large circle between two small circles. During the following years, farmers

in England found circles in their fields more and more often.

     The circles are called "crop circles" because they usually appear in fields of wheat or corn. The wheat in

the circles lies on the ground but is never broken; it keeps on growing, and the farmers can later harvest it.

Farmers always discover the crop circles in the morning, so the circles probably form at night. They appear

only in the months from May to September. What causes the crop circles?

     At first, people thought that some kids were making them as a joke, or that farmers were making them to

attract tourists.(In fact, in 1991, two men said they made the circles themselves, but many scientists don't

believe them.) People tried to copy them: They tried to make circles exactly like the ones the farmers had

found. They couldn't do it. They couldn't enter a field of wheat without leaving tracks, and they couldn't

flatten the wheat without breaking it.

     Several times people reported seeing stranger objects near the fields where crop circles later appeared.

Many people believe that these crop circles are the messages sent by living things from outer space (外层空间) or the marks left by their spaceships.

     Scientists who have studied the crop circles try to find out what causes them. In the summer of 1990

some scientists spent three weeks in the part of England where many circles have appeared. They had all the

latest high-tech equipment (最新高科技设备). The equipment-worth 1.8 million dollars-got nothing. But one

night, as the scientists were watching a field, crop circles formed in the field behind them, which were quite

different from the others. The scientists had neither seen nor heard anything.

     When Steven discovered the crop circles on his land in 1978, he said, "It was just like something that had

landed in the field from the air and gone back up again. I don't know what to make of these things."

     Crop circles have appeared in England, Japan, the United States and Russia. Experts from all over the

world have studied them, and they say what Steven said: They don't know what to make of these things.

1. "Flattened wheat" means ___________.

A. broken wheat

B. lying wheat

C. harvested wheat

D. growing wheat

2. The passage is mainly about something ___________.

A. that is done by living things from outer space

B. that cannot be solved but found all around the world

C. that cannot be made clear or understood

D. that is discovered and copied by the farmers