TOEFL Reading: ETS-TOEFL阅读机经 - 14S035GA3A3A851AL$

Which of the following is NOT mentioned in paragraph 4 as a way in which animals that graze as a herd benefit? A. Some animals in the herd will be in a position to observe danger while others have their heads down. B. Each animal in a herd tries to protect the others from danger. C. As a herd, animals can observe the landscape in a variety of directions at once. D. The movement of any animal away from potential trouble warns all of the other animals within the herd.