Paragraph                          Territoriality

1    In many species, members of the species exhibit aggressive behavior toward one another, often with a focus on territoriality, the fight for exclusive control of a particular area. The level of violence in territorial aggression varies widely from species to species, though few species fight other members of the species to death and instead rely on non-lethal contests for control of territory that involves noise-making maneuvers such as roaring or hissing or aggressive posturing or gestures.

2    Most bird species are known to be territorial to some degree, though the territorial behaviors exhibited by most species are limited to singing contests, which can go on for days, or threatening postures with wings lifted or extended. The swan, on the other hand, is quite unlike other birds in this respect. The swan may seem particularly elegant and serene as it glides across the surface of a lake; however, male swans are, in reality, quite territorial and will fight other male swans for the exclusive use of a lake no matter how large the lake is. Males will engage in ferocious contests, with their necks entwined as they attempt to cause mortal injury to each other.

15. Why does the author include the fight for exclusive control of a particular area in paragraph 1?

   (A) It presents an argument against a previously stated point.

   (B) It provides a definition of a previously stated term.

   (C) It presents a second area of focus of aggressive behavior.

   (D) It introduces a new idea to be further developed in the paragraph.

16. The author uses the word instead in paragraph 2 to show that the information that follows

   (A) contradicts what precedes it

   (B) expands upon what precedes it

   (C) provides an example of what precedes it

   (D) explains an effect of what precedes it

17. Why does the author mention singing contests in paragraph 2?

   (A) To demonstrate that birds create beautiful sounds

   (B) To provide an example of unusual behavior by birds

   (C) To show how violently aggressive some bird behavior is

   (D) To demonstrate that some types of territorial behaviors are not very aggressive

18. The author discusses the swan in paragraph 2 to provide an example of

   (A) a bird that makes threatening postures with its wings

   (B) a bird whose territorial behavior is extremely aggressive

   (C) non-lethal contests for control of territory

   (D) the limited aggressive behavior generally exhibited by birds

19. The author mentions their necks entwined in paragraph 2 in order

   (A) to indicate that swans are really rather affectionate

   (B) to emphasize how long swans' necks are

   (C) to make the point that the swans are only pretending to hurt one another

   (D) to create a mental image for the reader of fighting swans

正确答案：B_A_D_B_D