Directions: Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on the Answer Sheet with a single line through the centre. 

Questions 24 to 30 are based on the following passage:

Allelomimetic behavior may be defined as behavior in which two or more individual animals do the same thing, with some degree of mutual simulation and coordination. It can only involve in species with sense organs that are well enough developed so that continuous sensory contact can be maintained. It is found primarily in vertebrates(脊椎动物), in those species that are diurnal, and usually in those that spend much of their lives in the air, in open water or on open plains. In birds, allelomimetic behavior is the rule rather than the exception, though it may occasionally be limited to particular seasons of the year as it is in the redwing blackbird.

Its principal function is that of providing safety from predators(掠食者), partly because the flock can rely on many pairs of eyes to watch for enemies, and partly because if one bird reacts to danger, the whole flock is warned. Among mammals, allelomimetic behavior is very rare in rodents(啮齿动物), which almost never move in flocks or herds. Even when they are artificially crowded together, they do not conform in their movements. On the other hand, such behavior is a major system among large hoofed mammals,such as sheep. In the pack hunting carnivores(食肉类飞禽), allelomimetic behavior has another function of cooperative hunting for large prey(被捕食者) animals,such as moose.

Wolves also defend their dens as a group against larger predators, such as bears. Finally, allelomimetic behavior is highly developed among most primate groups, where it has the principal function of providing warning against predators,as though combined defensive behavior is also seen in troops of baboons(狒狒).

24. The main topic of the passage is the ____.

A) value of allelomimetic behavior in vertebrate and invertebrate species

B) definition and distribution of allelomimetic behavior

C) relationship of allelomimetic behavior to the survival of the fittest

D) personality factors that determine when an individual animal will show allelomimetic behavior

25. Which of the following places is the most likely setting for allelomimetic behavior?

A) A lake.

B) A cave.

C) An underground tunnel.

D) A thick forest.

26. The author implies that allelomimetic behavior occurs most often among a nimals that ____.

A) prey on other animals

B) are less intelligent than their enemies

C) move in groups

D) have one sense organ that dominates perception

27. Which of the following is the most clear example of allelomimetic?

A) Bears hunting for carnivores.

B) Cattle fleeing from a fire.

C) Horses running at a racetrack.

D) Dogs working with police officers.

28. According to the passage the primary function of allelomimetic behavior in bird is to ____.

A) defend nests against predators

B) look at each other

C) locate prey

D) warn against predators

29. According to the passage, what happens to the behavior of rodents when they are artificially crowded together?

A) Their allelomimetic behavior increases.

B) Continuous cooperation between them is maintained.

C) They become aggressive and attack each other.

D) They show little allelomimetic behavior.

30. Which of the following groups of human beings would probably show the greatest amount of allelomimetic behavior?

A) A group of students taking a test.

B) Tennis players competing in a tournament.

C) A patrol of soldiers scouting for the enemy.

D) Drivers waiting for a traffic light to change.