PASSAGE 2 – Questions 11-20

Many flower plants woo insect pollinators and gently direct them to their most fertile blossoms by changing the color of individual flowers from day to day. Through color cues, the plant signals to the insect that it would be better off visiting one flower on its bush than another. The particular hue the pollinator that the flower is full of far more pollen than neighboring blooms. That nectar-rich flower also happens to be fertile and ready to disperse its pollen or to receive pollen the insect has picked up from another flowers. Thus, the colored-coded communication system benefits both plants and insect.

For example, on the lantana plant, a flower starts out on the first day as yellow, when it is rich with pollen and nectar. Influenced by an as-yet-indentified environmental signal, the flower changes color by triggering the production of the pigment anthromyacin. It turns orange on the second day and red on the third. The the third day, it has no pollen to offer insects and is no longer fertile. On any given lantana bush, only 10 to 15 percent of the blossoms are likely to be yellow and fertile. But in tests measuring the responsiveness of butterflies, it was discovered that the insects visited the yellow flowers at least 100 times more than would be expected from haphazard visitation. Experiment with paper flowers and painted flowers demonstrated that the butterflies were responding to color cues rather than, say, the scene of the nectar.

In other types of plants, blossoms change from while to red, others from yellow to red, and so on. These color changes have been observed in some 74 families of plants.

Câu 11: The first paragraph of the passage implies that insects benefit from the color-coded communication system because ___________.

PASSAGE 3 – Questions 21-30

While many nineteenth-century reformers hoped to bring about reform through education or by eliminating specific social evils, some thinkers wanted to start over and remake society by founding ideal, cooperative communities. The United States seemed to them a spacious and unencumbered country where models of a perfect society could succeed. These communitarian thinkers hoped their success would lead to imitation, until communities free of crime, poverty, and other social ills would cover the land. A number of religious groups, notably the Shakers, practiced communal living, but the main impetus to found model communities came from nonreligious, rationalistic thinkers.

Among the communitarian philosophers, three of the most influential were Robert Owen, Charles Fourier, and John Humphrey Noyes Owen, famous for his humanitarian policies as owner of several thriving textile mills in Scotland, believed that faulty environment was to blame for human problems and that these problems could be eliminated in a rationally planned society. In 1825, he put his principles into practice at New Harmony, Indiana. The community failed economically after a few years but not before achieving a number of social successes. Fourier, a commercial employee in France, never visited the United States. However, his theories of cooperative living influenced many Americans through the writings of Albert Brisbane, who influenced many Americans through the writings of Albert Brisbane, who organized a series of self-sufficient associations or "phalanxes". One or more of these phalanxes was organized in every Northern state. The most famous were Red Bank, New Jersey, and Brook farm, Massachusetts. An early member of the latter was the author Nathaniel Hawthorne. Noyes founded the most enduring and probably the oddest of the utopian communities, the Oneida Community of upstate New York. Needless to say, none of these experiments had any lasting effects on the patterns of American society.

Câu 21: The main topic of the passage is ___________.

PASSAGE 4 – Questions 31-40

Lighthouses are towers with strong lights that help mariners plot their positions, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on island, reefs, and sandbars.

Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal had periods of darkness longer than periods of light, while an occulting signal's periods of light are longer. A group-lasting light gives off two or more flashes at regular intervals, and group-occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most light-houses are also equipped with radio beacons. The three types of apparatus used to produce the signals are catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.

In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock Light, look like wooden houses sitting on high platforms. Still others, such as the American Shoal Lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be confused in daylight, they can be distinguished by day-marker patterns- designs of checks and stripes painted in vivid colors on lighthouse walls.

In the past, the job of lighthouse keeper was lonely and difficult, if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with human supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outsides the United States. Some decommissioned lighthouses have been preserved as historical monuments.

Câu 31: Which of the following is NOT mentioned in the passage as one of the functions of lighthouses?