Natural flavorings and fragrances are often costlyand limited in supply. For example, the vitalingredient in a rose fragrance is extracted fromnatural rose oil at a cost of thousands of dollars apound; an identical synthetic substance can bemade for 1% of this cost. Since the early twentiethcentury, success in reproducing these substanceshas created a new industry that today produceshundreds of artificial flavors and fragrances.

　　Some natural fragrances are easily synthesized; these include vanillin, the aromaticingredient in vanilla, and benzaldehyde, the aromatic ingredient in wild cherries. Otherfragrances, however, have dozens, even hundreds of components. Only recently has it beenpossible to separate and identit3, these ingredients by the use of gas chromatography andspectroscopy. Once the chemical identity is known, it is often possible to synthesize them.Nevertheless, some complex substances, such as the aroma of fresh coffee, have still notbeen duplicated satisfactorily.

　　Many of the chemical compounds making up these synthetics are identical to those foundin nature, and are as harmless or harmful as the natural substances. New products must betested for safety, and when used in food, must be approved by the U.S. Food and DrugAdministration.

　　The availability of synthetic flavors and fragrances has made possible a large variety ofproducts, from inexpensive beverages to perfumed soap to used cars with applied "new carodor."

　　71. From the passage we can learn that ______

　　A. natural flavorings and fragrances are not quite dear

　　B. the limitation of natural flavorings and fragrances is clear

　　C. the supply of natural flavorings and fragrances is adequate to meet the demand

　　D. the cost of producing natural flavorings and fragrances is high

　　72. Which of the following is true according to the passage?

　　A. Natural rose fragrance is 100 times more expensive to produce than artificial rosefragrance.

　　B. The most important ingredient in a rose fragrance is obtained from natural rose oil at alow cost.

　　C. A different synthetic substance can be made for 1% of the cost.

　　D. Natural rose oil costs the same as its fragrances.

　　73. The industry of producing hundreds of artificial flavors and fragrances probablyappeared in ______

　　A. 2000 B. 1953

　　C. 1909 D. 1810

　　74. According to the passage, all the following are easier to synthesize EXCEPT ______

　　A. aromatic ingredient in vanilla

　　B. vanilla

　　C. aromatic ingredient in wild cherry

　　D. the flavor of fresh coffee

　　75. The underlined word "duplicated" in Paragraph 2 is closest in meaning to ______

　　A. make double

　　B. make a copy of

　　C. produce something equal to

　　D. take from

　　76. Why does the author mention fresh coffee in Paragraph 2?

　　A. As an example of complex substances having not been duplicated satisfactorily.

　　B. Because the coffee fragrance is hard to produce.

　　C. To conclude the passage.

　　D. The smell of fresh coffee is inviting.

　　77. ______ a substance can be synthesized.

　　A. Upon identifying the basic components of it

　　B. Once chemically analyzed

　　C. When gas chromatography is used

　　D. If spectroscopy is adopted

　　78. It can be inferred from the passage that ______

　　A. vanillin is easier to synthesize than benzaldehyde

　　B. not all synthetic flavors are harmless

　　C. in general, the less components there are in a fragrance, the harder it is to synthesize

　　D. synthesized substances must be tested for safety only if they are used in food

　　79. Which of the following is the best title for tile passage?

　　A. How to Synthesize Fragrances

　　B. Synthetic Substances Are Easy to Make

　　C. Natural Flavorings and Fragrances

　　D. Synthetic Flavors and Fragrances

　　80. Which of the following is NOT true according to the last paragraph?

　　A. Synthetic fragrances can be used to make a used car smell like a new one.

　　B. Synthetic flavors and fragrances have added to the varieties of products.

　　C. Lemon soap is made out of some delicious lemon.

　　D. It is likely that a bottle of orange juice is synthesized.

　　Some people associate migration mainly with birds. Birds do travel vast distances, butmammals also migrate. An example is the caribou, reindeer that graze on the grassy slopes ofnorthern Canada. When the weather turns cold, they travel south until spring. Their tracks areso well-worn that they are clearly visible from the air. Another migrating mammal is the Alaskafur seal. These seals breed only in the Pribilot Islands in the Bering Sea. The young are born inJune and by September are strong enough to go with their mothers on a journey of over 3,000miles. Together they swim down the Pacific Coast of North America. The females and youngtravel as far as southern California. The males do not journey so far. They swim only to the Gulfof Alaska. In the spring, males and females all return to the islands, and there the cycle beginsagain. Whales are among the greatest migrators of all. The humpback and blue whales migratethousands of miles each year from the polar seas to the tropics. Whales eat huge quantities ofplankton. These are most abundant in cold polar waters. In winter, the whales move to warmwaters to breed and give birth to their young.

　　81. From the passage we can learn that ______

　　A. people migrate like animals

　　B. only birds migrate

　　C. the female fur seals migrate only to the Gulf of Alaska

　　D. not all mammals migrate

　　82. The phrase "An example" underlined in Paragraph 1 refers to an example of a ______

　　A. migratory mammal

　　B. place where animals migrate

　　C. migrating bird

　　D. person who associates migration with birds

　　83. All the mammals are mentioned as migrating ones EXCEPT ______

　　A. caribou B. fin whale

　　C. reindeer D. Alaska fur seal

　　84. Where can you see from the air the migration of the mammals?

　　A. In the Pribilot Islands. B. In the Bering Sea.

　　C. In southern California. D. In northern Canada.

　　85. Which of the following is NOT true?

　　A. Whales breed in winter.

　　B. Young whales are given birth in cold waters.

　　C. Alaska fur seals give birth to the young only in one area.

　　D. Alaska fur seals are born in warm weather.

　　86. Together ______ of Alaska fur seals swim down the Pacific Coast of North America.

　　A. mothers and the young

　　B. fathers and the young

　　C. parents and the young

　　D. seals and whales

　　87. Which of the following is NOT described in the passage?

　　A. Whales migrate to breed and give birth to their young.

　　B. Whale-watching in Boston in summer is attracting.

　　C. Seals breed in the north before migration.

　　D. Reindeer feed on grass.

　　88. Whales live on ______

　　A. tiny plants and animals in the sea

　　B. the grassy slopes of northern Canada

　　C. their young in cold winter

　　D. the abundant seafood in tropic waters

　　89. How many kinds of migrating mammals are mentioned in the passage?

　　A. Four. B. Three.

　　C. Two. D. One.

　　90. What is the best title of the passage?

　　A. Three Types of Whales

　　B. Birds Migration

　　C. Mammals Also Migrate

　　D. Several Kinds of Migration