DEdmund Halley was an English scientist who lived over 200 years ago. He studied the obser

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Edmund Halley was an English scientist who lived over 200 years ago. He studied the observations of ets(彗星)which other scientists had made. The orbit of one particular et was a very difficult mathematical problem. He could not figure it out. Neither could other scientists who dealt with such problems.
However, Halley had a friend named Isaac Newton, who was a brilliant mathematician. Newton thought he had already worked out that problem, but he could not find the papers on which he had done it. He told Halley that the orbit of a et had the shape of an ellipse(椭圆形).
Now Halley set to work. He figured out(解决，计算出)the orbits of some of the ets that had been observed by scientists. He made a surprising discovery. The ets that had appeared in the years 1531, 1607, and 1682 all had the same orbit. Yet their appearance had been 75 to 76 years apart.
This seemed very strange to Halley. Three different ets followed the same orbit. The more Halley thought about it, the more he thought that there had not been three different ets as people thought. He decided that they had simply seen the same et three times. The et had gone away and had e back again.
It was an astonishing idea! Halley felt certain to make a prediction(预言)of what would happen in the future. He decided that this would appear in the year 1758. There were 53 years to go before Halley’s prediction could be tested. In 1758 the et appeared in the sky. Halley did not see it, for he had died some years before. Ever since then that et had been called Halley’s et, in his honor.
63. Edmund Halley figured out the orbit of     .
A. some different ets appearing several times
B. the same et appearing at different times
C. three different ets appearing at the same time
D. several ets appearing at the same time
64. Halley made his discovery     .
A. by doing experiments
B. by means of his own careful observation
C. by using the working of other scientists
D. by chance
65. Halley made a surprising, but correct prediction in the year    .
A. 1704          B. 1705     C. 1706           D. 1707
66. This passage in general is about     .
A. Halley and other scientists        B. the orbit of a et
C. Newton and Halley             D. Halley and his discovery63---66  BCBD