【小站原创】官方真题Official42托福阅读文本及答案解析（Callisto and Ganymede）
- 2016年05月10日10:08 来源：小站教育作者：小站托福编辑
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Callisto and Ganymede
From 1996 to 1999, the Galileo spacecraft passed through the Jovian system, providing much information about Jupiter's satellites. Callisto, the outermost of Jupiter's four largest satellites, orbits the planet in seventeen days at a distance from Jupiter of two million kilometers. Like our own Moon. Callisto rotates in the same period as it revolves, so it always keeps the same face toward Jupiter. Its noontime surface temperature is only about -140°C, so water ice is stable on its surface year-round. Callisto has a diameter of 4.820 kilometers, almost the same as that of Mercury. Its mass is only one-third as great, which means its density must be only one-third as great as well. This tells us that Callisto has far less of the rocky metallic materials found in the inner planets and must instead be an icy body through much of its interior.
1. According to paragraph 1, which of the following statements about Callisto is true?
A. It is the satellite closest to Jupiter's surface
B. Its surface temperature is constant at all times of the day.
C. It has the same mass and diameter as the planet Mercury
D. It completes one rotation every seventeen days.
解析：根据原文Callisto, the outermost of Jupiter's four largest satellites, orbits the planet in seventeen days at a distance from Jupiter of two million kilometers.可知，orbits the planet in seventeen days at a distance from Jupiter 对应D选项中的one rotation every seventeen days. 所以D选项正确。