首页
登录
职称英语
Natural flavorings and fragrances are often costly and limited in supply. Fo
Natural flavorings and fragrances are often costly and limited in supply. Fo
游客
2024-01-01
10
管理
问题
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." [br] Why does the author mention fresh coffee in Paragraph 2?
选项
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.
答案
A
解析
推断题型。见上题推理:作者之所以提及新鲜咖啡,是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。所以选项A为答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3325557.html
相关试题推荐
Physics,oneofthenaturalsciences,______energyandmatter.A、dealwithB、are
AcollegegraduatewhoAistrainedinoneofthenaturalBsciencesormathematic
Manypartsoftheworldarelosingimportantnaturalresources,suchasforests,a
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Thefirstrecordeduseofnaturalgastolightstreetlampsitwasinthetowno
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
随机试题
【B1】[br]【B9】A、puzzledB、contrastedC、doubledD、mixedD词义辨析题。回自己故乡的想法对于难民来说,既想回
电流对人体的伤害主要包括()。A.电击和电伤 B.触电和电击 C.触电和电伤
A.多食肥甘厚味 B.产后、外伤、术后长期卧床 C.长期站立、从事重体力劳动
土豆∶薯片∶淀粉A.牛奶∶奶粉∶蛋白质 B.高粱∶白酒∶酒精 C.棉花∶毛巾
人在每一瞬间,将心理活动选择了某些对象而忽略了另一些对象。这一特点指的是注意的(
经党中央同意,中央精神文明建设指导委员会将()定为“公民道德宣传日”。 A.
第55题答案是__________A.reported B.predicted
工程量清单的用途是为()使用。A.工程结算 B.招标人参考 C.投标人报价
根据《民法典》的规定,施工企业从银行借款时可以作为抵押物的有()。A.施工企业所
机械台班幅度差是指在施工定额中所规定的范围内没有包括,而在实际施工中又不可避免产
最新回复
(
0
)