题目内容：

D

A mysterious machine found in a 2,000-year-old Greek shipwreck may have been used to calculate the positions of planets, predict when eclipses (日、月蚀) were to occur, and study other parts of astronomy (天文学). When it was found underwater about 100 years ago, the machine was in poor shape. Its metal pieces had become one mass (堆), and then broke into pieces.

When the researchers began to study what was left of the machine, they thought it might have something to do with astronomy. To find out more, they recently used advanced imaging methods, including X-ray computer tomography (断层摄影术), to look inside the metal parts and to check for ancient writing on the machine.

According to their research, the researchers believed that this machine could have been used to compute eclipses of the sun and moon and was also able to show the movements of planets. A user could pick a day in the future and, work out a planet’s position on that date by moving some sort of crank (曲柄) on the machine.

Besides, the researchers discovered that the machine had at least 30 bronze gears (齿轮) with as many as 225 teeth, likely all cut by hand.

With all the collected information, the researchers came up with a new model for how the machine operated. The model has 29 of the 30 known gears and five more that were probably there but never found. Also，the new picture adds a previously undiscovered spiral dial (螺旋刻度盘) to the back of the machine near the bottom. A hand moving around the dial could have pointed to eclipses over a period of 18 years.

71. The passage is most probably taken from _____.

A. a short-story collection

B. a popular science magazine

C. a political report

D. an old personal diary

72. What is the passage mainly about?

A. New research on calculating the positions of planets.

B. A popular way of computing eclipses of the sun and moon.

C. Scientists’ interest in the secrets of a 2,000-year-old Greek shipwreck.

D. A mysterious machine which could be used for astronomical research.

73. What do we learn from the third paragraph of the passage?

A. The machine might have been used to calculate the positions of the planets.

B. Scientists made great progress in predicting eclipses of the sun and moon.

C. The researchers discovered some secrets in the Greek shipwreck.

D. The machine can be of great help for people working out the sizes of planets.

74. The researchers made a new model because they____.

A. wished to repair the broken machine

B. wanted to study the shipwreck more conveniently

C. hoped to know how the machine worked

D. expected it to be used in modern scientific research

75. Which of the following statements is TRUE about the old machine?

A. It has 35 gears on it.

B. It has a spiral dial.

C. It was invented about 100 years ago.

D. Its gears have many teeth.