[請益] Planets in Our Solar System

看板TOEFL_iBT (TOEFL_iBT托福)作者justinkay (夢想～～)時間15年前 (2011/06/25 18:12)推噓1(1推 0噓 2→)

留言3則, 2人參與討論串1/1

想請教各位大大一個題目， Paragraph 5: The Jovian planets have very thick atmospheres consisting of varying amounts of hydrogen, helium, methane, and ammonia. By comparison, the terrestrial planets have meager atmospheres at best. A planet's ability to retain an atmosphere depends on its temperature and mass. Simply stated, a gas molecule can "evaporate" from a planet if it reaches a speed known as the escape velocity. For Earth, this velocity is 11 kilometers per second. Any material, including a rocket, must reach this speed before it can leave Earth and go into space. The Jovian planets, because of their greater masses and thus higher surface gravities, have higher escape velocities (21-60 kilometers per second) than the terrestrial planets. Consequently, it is more difficult for gases to "evaporate" from them. Also, because the molecular motion of a gas depends on temperature, at the low temperatures of the Jovian planets even the lightest gases are unlikely to acquire the speed needed to escape. On the other hand, a comparatively warm body with a small surface gravity, like Earth's moon, is unable to hold even the heaviest gas and thus lacks an atmosphere. The slightly larger terrestrial planets Earth, Venus, and Mars retain some heavy gases like carbon dioxide, but even their atmospheres make up only an infinitesimally small portion of their total mass. 6. According to paragraph 5, which of the following statements is true of both Jovian and terrestrial planets? ○ The thicker the atmosphere, the smaller the planet’s mass ○ The more varied the gases in the atmosphere, the higher the temperature ○ The higher the surface gravity, the higher the escape velocity ○ The less the atmosphere contributes to the total mass, the lower the temperature 請問這個題目答案為什麼選 C ? 因為題目有提到 is true of both Jovian and terrestrial planets 不是單獨只有問 Jovian。謝謝！！ -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 111.235.228.237