GRE Reading Comprehension: Maggoosh-GRE阅读Maggoosh - RZ67VGD570D322V7M

It can be inferred from the passage that Zwicky hypothesized the existence of "dark matter" in order to account for A. the speed in which galaxies are moving away from one another B. the manner in which large galaxies tend to clump together C. the great distance between certain galaxies D. a phenomenon that visible matter alone is unable to explain E. the behavior of galaxies outside of great clusters