GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - 2530455PSO1214C7J

The passage mentions which of the following as an obstacle to verify the "prediction" mentioned in the passage? A. Wounds to the mane area are often difficult to observe. B. Only a few lion populations have been well studied. C. The severity of fights between lions is difficult to determine. D. Individual males seldom have strong distinguishing characteristics. E. Researchers have relatively few opportunities to observe lion populations directly.