In paragraph 4, why does the author point out that Mars has few ancient craters that are less than 5 kilometers in diameter? A. To explain why scientists believe that the surface matter filling Martian craters is mostly dust B. To explain why scientists believe that the impact craters on Mars were created by meteoroids C. To support the claim that the Martian atmosphere is an efficient erosive agent D. To argue that Mars experienced fewer ancient impacts than the Moon did