[Reading Comprehension]
试题详情
文章:
Line | Io and Europa, the inner two of Jupiters four |
largest moons, are about the size of Earths moon | |
and are composed mostly or entirely of rock and | |
metal. Ganymede and Callisto are larger and roughly | |
(5) | half ice. Thus, these four moons are somewhat |
analogous to the planets of the solar system, in which | |
the rock- and metal-rich inner planets are distinct | |
from the much larger gas- and ice-rich outer planets. | |
Jupiters moons are, however, more systematic: | |
(10) | many of their properties vary continuously with |
distance from Jupiter. For example, Io is ice-free, | |
Europa has a surface shell of ice, and while | |
Ganymede and Callisto are both ice-rich, outermost | |
Callisto has more. | |
(15) | This compositional gradient has geological |
parallels. Io is extremely geologically active, Europa | |
seems to be active on a more modest scale, and | |
Ganymede has undergone bouts of activity in its | |
geological past. Only Callisto reveals no geological | |
(20) | activity. In similar fashion, Callistos surface is very |
heavily cratered from the impact of comets and | |
asteroids; Ganymede, like Earths moon, is heavily | |
cratered in parts; Europa is very lightly cratered; and | |
no craters have been detected on Io, even though | |
(25) | Jupiters gravity attracts comets and asteroids |
passing near it, substantially increasing the | |
bombardment rate of the inner moons compared | |
to that of the outer ones. But because of Ios high | |
degree of geological activity, its surface undergoes | |
(30) | more-or-less continuous volcanic resurfacing. |
题目:
According to the passage, the difference in the amount of cratering on Callistos and Ios respective surfaces can probably be explained by the difference between these two moons with respect to which of the following factors?
选项:
A、Size
B、Ice content
C、The rate of bombardment by comets and asteroids
D、The influence of Jupiters other moons
E、The level of geological activity
答案:
E