GRE Reading Comprehension: Maggoosh-GRE阅读Maggoosh - Q5158QQV8E8TX6EAM

The author suggests that at least some of "a number of difficult problems..." can be understood by A. extrapolating from observable phenomena B. anticipating the result of the collision of small bodies C. studying the rate of accretion on planets D. observing the internal process of planets E. discounting the dynamics of how orbits change over time