Sometimesveryoddthingsshowupinordinaryplaces.Inthe1800s...

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问题详情：

Sometimes very odd things show up in ordinary places. In the 1800s, a strange sight began to be reported by farmers. Then in the 1970s, this strange event began to happen more and more often. People traveled for miles to stand in the fields and take photos of something they couldn't easily explain. What were they looking at? It was the crop circles — large and complex designs set into the middle of ordinary farm field. No one could understand how these huge designs were made.

Crop circles are found most often in fields of wheat, corn, or rice. They are usually created overnight, although some are reported to have appeared during the day. They have been seen all around the world, in more than 70 different countries. Scientists have found that the plants inside a crop circle are drier than the ones outside it. The plant stems (茎) are bent and not broken in most crop circles, and sometimes the soil in the design has more iron than the soil outside of the design. Unfortunately, these facts alone do not help scientists answer their questions about crop circles. These facts only make them more mysterious.

Some people believe crop circles are made by UFOs (Unidentified Flying Objects) landing in farm fields. Others think aliens are leaving us messages in the beautiful designs. Still others believe Earth energy under the ground makes plants bend over in designs. Some people say they actually made the crop circles with special equipment. Scientists have found some crop circles that are certainly made by people, but they are usually a little different from other crop circles. So who makes crop circles and why they make them can't be explained to this very day.

32. It's generally thought that crop circles _____.

A. have very frightening designs

B. happen in the same places

C. are found in terrible places

D. are made during the night

33. What happens to the paints inside the crop circles?

A. They are broken.

B. They die very soon.

C. They are bent.

D. They need little water.

34. Which of the following have the scientists proved?

A. Earth energy is one reason for crop circles' appearance.