单选题 Natural flavorings and fragrances are often costly and limited in supply. For example, the vital ingredient in a rose fragrance is extracted from natural rose oil at a cost of thousands of dollars a pound; an identical synthetic substance can be made for 1% of this cost. Since the early twentieth century, success in reproducing these substances has created a new industry that today produces hundreds of artificial flavors and fragrances.
Some natural fragrances are easily synthesized; these include vanillin, the aromatic ingredient in vanilla, and benzaldehyde, the aromatic ingredient in wild cherries. Other fragrances, however, have dozens, even hundreds of components. Only recently has it been possible to separate and identify these ingredients by the use of gas chromatography and spectroscopy. 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 not been duplicated satisfactorily.
Many of the chemical compounds making up these synthetics are identical to those found in nature, and are as harmless or harmful as the natural substances. New products must be tested for safety, and when used in food, must be approved by the U.S. Food and Drug Administration.
The availability of synthetic flavors and fragrances has made possible a large variety of products, from inexpensive beverages to perfumed soap to used cars with applied "new car odor."

单选题 From the passage we can learn that ______.

单选题 Which of the following is TRUE according to the passage?

A、 Natural rose fragrance is 100 times more expensive to produce than artificial rose fragrance.
B、 The most important ingredient in a rose fragrance is obtained from natural rose oil at a low cost.
C、 A different synthetic substance can be made for 1% of the cost.
D、 Natural rose oil costs the same as its fragrances.

【正确答案】 A

【答案解析】[解析] 本题考查是非判断。根据文章第一段第二句“For example, the vital ingredient in a rose fragrance is extracted from natural rose oil at a cost of thousands of dollars a pound; an identical synthetic substance can be made for 1% of this cost.”可知，玫瑰香(料)的主要成分是从天然玫瑰油中萃取的，这种萃取物一磅价值数千美元；而人工合成的玫瑰香料价值只是天然香料的百分之一。所以，答案是A。

单选题 The industry of producing hundreds of artificial flavors and fragrances probably appeared in ______.

【正确答案】 C

【答案解析】[解析] 本题考查细节理解。根据文章第一段第三句“Since the early twentieth century, Success in reproducing these substances has created a new industry that today produces hundreds of artificial flavors and fragrances.”可知，生产成百上千种人工调味品和香料的时间是二十世纪早期。四个选项中，只有C项1909符合“二十世纪早期”这一时间。所以，答案是C。

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

【正确答案】 D

【答案解析】[解析] 本题考查细节理解。根据文章第二段第一句“Some natural fragrances are easily synthesized; these include vanillin, the aromatic ingredient in vanilla, and benzaldehyde, the aromatic ingredient in wild cherries.”可知，A、B、C三项在文中均有提及，故可排除。因此，答案是D。

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

【正确答案】 C

【答案解析】[解析] 本题考查推理判断。根据文章第二段前几句得知：“Some natural fragrances are easily synthesized. Other fragrances, however, have dozens, even hundreds of components...it is often possible to synthesize them. Nevertheless, some complex substances, such as the aroma of fresh coffee, have still not been duplicated satisfactorily.”可知，有些天然香料可以很容易进行人工合成。而有些却包含有几十甚至上百种成分——言外之意，较难合成。只是到了最近，由于使用气相色谱分析和分光镜才能分离或鉴别出这些成分。一旦分析出其化学成分，人们就有可能将之合成。然而仍有一些复杂的成分，如新鲜咖啡的香味难以合成得令人满意。由此可推断出很难合成与新鲜咖啡香味相同的香料。选项C内容与此意最接近。所以，答案是C。

单选题 Why does the author mention fresh coffee in Paragraph 2?

【正确答案】 A

【答案解析】[解析] 本题考查推理判断。根据语境可知，然而仍有一些复杂的成分，如新鲜咖啡的香味难以合成得令人满意。所以，作者之所以提及新鲜咖啡，是要借此例来说明一些成分复杂的物质很难令人满意地合成出来。因此，答案是A。

单选题 ______, a substance can be synthesized.

【正确答案】 B

【答案解析】[解析] 本题考查细节理解。根据文章第二段倒数第二句“Once the chemical identity is known, it is often possible to synthesize them.”可知，一旦分析出其化学成分，人们就有可能将之合成。所以，答案是B。

单选题 It can be inferred from the passage that ______.

【正确答案】 B

【答案解析】[解析] 本题考查推理判断。根据文章三段第一句“Many of the chemical compounds...and are as harmless or harmful as the natural substances.”可知，由此推断出：很多化学合成物(其中包括香料)与其自然界存在的物质一样是无害的。所以，答案是B。

单选题 Which of the following is the best tide for the passage?

【正确答案】 D

【答案解析】[解析] 本题考查主旨大意。通读全文可知，文章开头便指出天然调味品和香料供应有限且价格不菲，后来就产生了人工合成品，尽管有些合成容易，但也有些很难合成，但人工合成使大量生产成为可能；其中主要讨论人工合成品(调味品和香料)。所以。答案是D。

单选题 Which of the following is NOT true according to the last paragraph?

【正确答案】 C

【答案解析】[解析] 本题考查细节理解。根据“The availability of synthetic flavors and fragrances has made possible a large variety of products”可知A、D两项正确；根据“from inexpensive beverages to perfumed soap to used cars with applied "new car odor."”可知，B项正确。只有C项内容未被提及，柠檬属于natural substance，不是人工合成物。所以，答案是C。