Contains a large volume of dust, soil and boulders

Suggests that liquid once came out of the surface at the crater site

Was thrown a comparatively long distance from the center of the crater

13、Look at the four squares [■] that indicate where the following sentence could be added to thepassage.

This surface feature has led to speculation about what may lie under Mars's surface.

Where would the sentence best fit? Click on a square to add the sentence to the passage.

Paragraph 6

The detailed appearance of Martian impact craters provides an important piece of information about conditions just below the planet's surface. Martian craters are surrounded by ejecta (debris formed as a result of an impact) that looks quite different from its lunar counterparts. A comparison of the Copernicus crater on the Moon with the (fairly typical) crater Yuty on Mars demonstrates the differences. The ejecta surrounding the lunar crater is just what one would expect from an explosion ejecting a large volume of dust, soil, and boulders. ■ However, the ejecta on Mars gives the distinct impression of a liquid that has splashed or flowed out of crater. ■ Geologists think that this fluidized ejecta crater indicates that a layer of permafrost, or water ice, lies just a few meters under the surface. ■ Explosive impacts heated and liquefied the ice, resulting in the fluid appearance of the ejecta. ■

B

14、 Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Volcanoes and impact craters are major features of Martian geology.

A.     Plate motion on Mars, once considered to have played no role in shaping the planets surface, isnow seen as being directly associated with the planet's earliest volcanoes.

B．Mars has shield volcanoes, some of which are extremely tall because of the planet"s low surfacegravity.

C. Although the erosive power of the Martian atmosphere ensures that Mars has fewer craters than theMoon does, impact craters are prominent on Mars' s surface.

D. Scientists cannot yet reliably estimate the age of the Martian surface because mere has been too

much erosion of it.

E. Scientists have been surprised to discover that conditions just below the surface of Mars are verysimilar to conditions just below the surface of the Moon

F. Studies of crater ejecta have revealed the possibility of a layer of permafrost below the surface ofMars.