The smooth operation of an ant colony depends on ten to twenty different signals,

　　most of which are pheromones (chemical signals triggering behavioral responses). It is

　　estimated that red fire ants employ at least twelve different chemical signals. The simples

　　Line of these is the carbon dioxide from the respiration of an ant cluster, a chemical that acts as

　　(5)  a pheromone to promote aggregation. Workers move toward a source of carbon dioxide,

　　resulting in solitary ants moving to join a group. At the other extreme, the most complex

　　of the fire ants' signals is probably colony odor, by which the workers of a particular

　　colony or nest identify another worker as local or foreign. Each ant nest has its own odor

　　as a result of its location, history, and local food supply. The resident ants pick up this

　　(10) odor on their bodies, so that ants of the same species, but from different nests, have

　　different colony odors. This allows ants to identify intruders and maintain colony

　　integrity.

　　Fire ants also make use of an alarm pheromone to alert workers to an emergency,

　　and their scouts lay down a trail pheromone as a guide during mass migrations. A fire ant

　　(15) queen emits a chemical signal that identifies her to the colony's workers. They respond

　　by scurrying to gather around her. The decomposing corpse of a dead ant also generates

　　a signal, to which workers respond by eliminating the corpse from the nest.

　　Ants provide examples of both public (accessible to other species) and private

　　messages. One of their most important private messages concerns food, for a food source

　　(20) is worth keeping secret. Each species marks its trails with signals that are meaningless to

　　others, so that an ant crossing a trail left by another ant species typically notices nothing.

　　On the other hand, a secret signal to mark a dead body is unnecessary. Many kinds of ants

　　perceive a natural decomposition product of dead insects as a signal to remove a corpse.

　　If an outsider recognizes this message and moves the body, no harm is done.

　　30. What aspect of ants does the passage mainly discuss?

　　(A) The relationship between the queen and the worker ants

　　(B) Ways in which ants use chemical signals

　　(C) Methods ants use to identify food sources

　　(D) The importance of respiration in the production of ant pheromones

　　31. The phrase "smooth operation" in line 1 is closest in meaning to

　　(A) daily activity

　　(B) effective functioning

　　(C) delicate balance

　　(D) permanent location

　　32. According to the passage, carbon dioxide serves which of the following functions for fire ants?

　　(A) It protects the queen.

　　(B) It attracts other ant species.

　　(C) It informs workers of possible danger.

　　(D) It encourages the ants to gather together.

　　33. The word "cluster" in line 4 is closest in meaning to

　　(A) organ

　　(B) activity

　　(C) group

　　(D) cycle

　　34.According to the passage, each nest has a distinct odor that allows its inhabitants to

　　(A) find the location of the nest in the dark

　　(B) distinguish worker ants from other ants

　　(C) distinguish foreign ants from resident ants

　　(D) signal other inhabitants when foreign ants attack

　　35. The word "alert" in line 13 is closest in meaning to

　　(A) allow

　　(B) transport

　　(C) ware

　　(D) provide

　　36. What is the role of pheromones in the mass migrations of ants?

　　(A) Pheromones are used to create a trail that directs the ants during migrations.

　　(B) Pheromones signal the ants that the nest has been invaded and must be

　　abandoned.

　　(C) Pheromones control the speed at which ants move from one location to another.

　　(D) Pheromones enable scouts to identify suitable areas for establishing a new nest.

　　37. The word "scurrying" in line 16 is closest in meaning to

　　(A) agreeing

　　(B) appearing

　　(C) competing

　　(D) rushing

　　38. The word "others" in line 21 refers to

　　(A) private messages

　　(B) species

　　(C) trails

　　(D) signals

　　39. Why does the author mention "dead insects" in line 23 ?

　　(A) To compare the social behaviors of ants with those of other insects

　　(B) To emphasize the dangers that all insects encounter

　　(C) To argue the superiority of ants over other insects

　　(D) To indicate a behavior that is common among various kinds of ants

　　40. Which of the following terms is defined in the passage?

　　(A) pheromones (line 2)

　　(B) colony integrity (lines 11-12)

　　(C) mass migrations (line 14)

　　(D) private messages (lines 18-19)

　　Questions 41-50

　　The Homestead Act of 1862 gave beads of families or individuals aged twenty-one or

　　older the right to own 160 acres of public land in the western United States after five years

　　of residence and improvement. This law was intended to provide land for small farmers

　　Line and to prevent land from being bought for resale at a profit or being owned by large

　　(5)  landholders. An early amendment to the act even prevented husbands and wives from

　　filing separate claims. The West, land reformers had assumed, would soon contain many

　　160-acre family farms.

　　They were doomed to disappointment. Most landless Americans were too poor to

　　become farmers even when they could obtain land without cost. The expense of moving a

　　(10) family to the ever-receding frontier exceeded the means of many, and the cost of tools,

　　draft animals, a wagon, a well, fencing, and of building the simplest house, might come

　　to $1,000——a formidable barrier. As for the industrial workers for whom the free land was

　　supposed to provide a "safety valve," they had neither the skills nor the inclination to

　　become farmers. Homesteaders usually came from districts not far removed from frontier

　　(15) conditions. And despite the intent of the law, speculators often managed to obtain large

　　tracts. They hired people to stake out claims, falsely swear that they had fulfilled the

　　conditions laid down in the law for obtaining legal title, and then deed the land over to

　　their employers.

　　Furthermore, 160 acres were not enough for raising livestock or for the kind of

　　(20) commercial agriculture that was developing west of the Mississippi. The national

　　government made a feeble attempt to make larger holdings available to homesteaders

　　by passing the Timber Culture Act of 1873, which permitted individuals to claim an

　　additional 160 acres if they would agree to plant a quarter of it in trees within ten years.

　　This law proved helpful to some farmers in the largely treeless states of Kansas,

　　(25) Nebraska, and the Dakotas. Nevertheless, fewer than 25 percent of the 245,000 who

　　took up land under the Act obtained final title to the property.

　　41. Which aspect of the Homestead Act of

　　1862 does the passage mainly discuss?

　　(A) How it transformed the western United States into a place of small farms

　　(B) Why it was an improvement over previous attempts at land reform

　　(C) Why it did not achieve its aim to provide land for small farmers

　　(D) How it failed in the largely treeless states of Kansas, Nebraska, and the Dakotas

　　42. An amendment added to the Homestead Act of 1862 specified that

　　(A) five years of residence was required for landownership

　　(B) husbands and wives could not file separate claims

　　(C) the price of 160 acres of land was $1,000

　　(D) land could not be resold for a profit

　　43. The word "formidable" in line 12 is closest in meaning to

　　(A) obvious

　　(B) predictable

　　(C) difficult

　　(D) manageable

　　44. It can be inferred that the "safety valve" in line 13 refers to

　　(A) a new kind of machinery

　　(B) an alternative for urban workers

　　(C) an area in a factory

　　(D) a procedure designed to protect workers

　　45. The word "intent" in line 15 is closest in meaning to

　　(A) purpose

　　(B) power

　　(C) effect

　　(D) invention

　　46. According to the passage, why did the government pass the Timber Culture Act of 1873 ?

　　(A) To make larger tracts of land available to small farmers

　　(B) To settle Kansas, Nebraska, and the Dakotas

　　(C) To encourage land speculation west of the Mississippi

　　(D) To increase the variety of trees growing in the western states

　　47. The word "they"in line 23 refers to

　　(A) larger holdings

　　(B) individuals

　　(C) 160 acres

　　(D) trees

　　48. According to the passage, how many of the farmers who settled land under the Timber Culture

　　Act of 1873 received final title to the property?

　　(A) Fewer than 25%

　　(B) More than 160

　　(C) 10% per year

　　(D) 245,000

　　49. The passage mentions all of the following as reasons the Homestead Act of 1862 did not

　　achieve its aims EXCEPT:

　　(A) Most landless Americans could not afford the necessary tools and provisions.

　　(B) Industrial workers lacked the necessary fanning skills.

　　(C) The farms were too large for single families to operate successfully.

　　(D) Homesteaders usually came from areas relatively close to the frontier.

　　50. Which of the following can be inferred from the passage about the Timber Culture Act of 1873?

　　(A) It especially helped farmers with large holdings of land.

　　(B) It was most important to farmers living in states that had plenty of trees.

　　(C) The majority of farmers did not benefit significantly from it.

　　(D) The majority of farmers did not need the extra 160 acres it provided.

　　TWE

　　When people move to another country, some of them decide to follow the customs of the new

　　country. Others prefer to keep their own customs. Compare these two choices. Which one do you prefer? Support your answer with specific details.

　　0205 answer

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