TOEFL Reading: ETS-TOEFL阅读机经 - 21L6EKKG18ZS3LS3L$

Grazing in a herd rather than as solitary individuals decreases the risk to grazers from predators. A. If a grazer can spot a predator before it actually attacks, the grazer has a very good chance of getting away and since grasslands provide little cover for predators, the grazer always has the advantage. B. Hunters can attack only one grazer at a time, and where there are many animals moving back and forth and grazing together in a herd, it is difficult for hunters to maintain their focus on a single target. C. When a member of a herd wanders away from the others or falls behind as the herd runs from danger, a hunter who manages to get between it and the herd stands a good chance of making a kill. D. A grazer cannot watch for danger while feeding, so predators can use those moments gradually to approach a solitary animal unobserved, but in a herd there will always be some animals on alert. E. When a herd of grazers spots the approach of a solitary hunter, it may run toward the hunter, which generally causes it to abandon the chase, but predators hunting as a pack are not so easily driven away. F. After a herd of running animals sees that the hunters pursuing it have stopped, the herd tries to help members