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
2025-02-02
12
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/3940117.html
相关试题推荐
Thefirstrecordeduseofnaturalgastolightstreetlampsitwasinthetowno
Thefirstrecordeduseofnaturalgastolightstreetlampsitwasinthetowno
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
With2005fastbecoming"theyearofthenaturaldisaster",itistimetore
With2005fastbecoming"theyearofthenaturaldisaster",itistimetore
With2005fastbecoming"theyearofthenaturaldisaster",itistimetore
With2005fastbecoming"theyearofthenaturaldisaster",itistimetore
With2005fastbecoming"theyearofthenaturaldisaster",itistimetore
随机试题
Areyougoingtofixthecaryourself,orareyougoingtohaveit______?A、fixi
Thereare10blanksinthepassage.Usethewords(phrases)giveninthebox
[originaltext]W:Hi,thisisJane.We’rebackfromtheholiday.Comeoverandv
制定健康教育计划时,确定优先项目应遵循的原则包括重要性原则和()。
安静状态下,成人脑血流量占心排出量的多少A.5% B.20% C.10%
气体的分压是指A.混合气体中某一种气体的压力 B.空气的压力 C.混合气体的
地陪不能一同住在饭店时,应将自己的联系方式告知()A:领队 B:全陪 C:旅
某二级公路,其中一段路堤通过湖塘一角,长度51m,该路段地基软土厚度0.5m左右
房地产抵押贷款中,商业银行与借款人签订的房地产抵押合同,属于( )。A、单务
以下哪种因素与牙周病关系不大A.银汞合金充填物有悬突 B.牙齿排列不齐 C.
最新回复
(
0
)