At first，people thought that the circles were a hoax.Probably young people were making them as a joke，or farmers were making them to attract tourists.To prove that the circles were a hoax，people tried to make circles exactly like the ones that farmers had found.They couldn’t do it.They couldn’t enter a field of grain without leaving tracks，and they couldn’t flatten the grain without breaking it.

　　Many people believe that beings from outer space are making the circles to communicate with us from far away and that the crop circles are messages from them.

　　Scientists who have studied the crop circles suggested several possibilities.Some scientists say that a downward rush of wind leads to the formation of the circles—the same downward rush of air that sometimes causes an airplane to crash.Other scientists say that forces within the earth cause the circles to appear.There is one problem with all these scientific explanations：crop circles often appear in formations，like the five-dot formation.It is hard to believe that any natural force could form those.

　　1．In the summer of 1978，an English farmer discovered in his field that ________.

　　A．some of his wheat had been damaged

　　B．some of his wheat had fallen onto the ground

　　C．his grain was growing up in circles

　　D．his grain was moved into several circles

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