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 ______.
【正确答案】
D
【答案解析】[分析] 细节题型。
见第一段第一句：Natural flavorings and fragrances are often costly and limited in supply．因此选项D为答案。
单选题
Which of the following is true according to the passage?
【正确答案】
A
【答案解析】[分析] 是非题型。
见第一段第二句的后半部分：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．意即：玫瑰香(料)所需的成分是从天然玫瑰油中萃取的，这种萃取物一磅价值要数千美元；而人工合成的玫瑰香料价值只是天然的百分之一。因此选项A为答案。
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】[分析] 细节题型。
见第一段第三句：Since the early twentieth century，success in reproducing these substances has created a new industry that…符合“二十世纪早期”条件的选项只有C，所以是答案。
单选题
According to the passage, all the following are easier to synthesize EXCEPT ______.
【正确答案】
D
【答案解析】[分析] 细节题型。
本题可用排除法。见第二段第一句：Some natural fragrances are easily synthesized； these include vanillin，the aromatic ingredient in vanilla，and benzaldehyde，the aromatic ingredient in wild cherries．选项A、B、C的内容均被提及，因此除外的选项只有D，所以D为答案。(本题答案也可用下一题的推断法推出)
单选题
The underlined word "duplicated" in Paragraph 2 is closest in meaning to ______.
【正确答案】
C
【答案解析】[分析] 推断题型。
从第二段前几句得知：Some natural fragrances are easily synthesized．(有些天然香料可以很容易地进行人工合成。)Other fragrances，however，have dozens， even hundreds of components．(而有些却包含有几十甚至上百种成分——言外之意，较难合成。)Only recently has it been possible to separate and identify these ingredients by the use of gas chromatography and spectroscopy．(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。)Once the chemical identity is known，it is often possible to synthesize them．(一旦了解了它们的化学成分，人们就有可能将之合成。)Nevertheless, some complex substances, such as the aroma of fresh coffee．have still not been duplicated satisfactorily．(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，所以是答案。
单选题
Why does the author mention fresh coffee in Paragraph 2?
单选题
It can be inferred from the passage that ______.
【正确答案】
B
【答案解析】[分析] 推断题型。
见第三段第一句：Many of the chemical compounds…and are as harmless or harmful as the natural substances．由此推断出；有些化学合成物(其中也包括香料)与其自然界存在的物质一样是无害的，有些则是有害的。因此选项B为答案。
单选题
Which of the following is the best title for the passage?