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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 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 [判断题]询问与倾听是接警员依据询问要素引导报警人以问答的方式，快速掌握灾情信息的基本方法。接警员询问时应把握询问要素，专注耐心地倾听报警人的语气或语速等语言环境，对周围情况准确做出判断。
A.正确 B.错误 [判断题]地震灾害救援中,从建筑废墟高处利用绳索系统向下转移伤员时,应充分考虑锚点的稳固性。( )
A.正确 B.错误 [单选题]二次侧电流为5A的单相电流互感器额定容量为10VA，则其额定阻抗为（）。
A.0.4Ω B.1Ω C.2Ω D.5Ω [单项选择]重症肌无力患者禁用的药物是（）
A. 氢氯嚷嗪（双氢克尿塞） B. 肾上腺皮质激素 C. 麻黄碱 D. 环磷酰胺 E. 氨基糖苷类抗生素 [单选题]下列几种物质，以( )的导热本领最大。
A.钢 B.铝 C.铜 D.塑料 [多选题]我国《妇女权益保障法》所保障的男女平等的权益包括下列哪些?
A.政治权利 B. 文化教育权益 C. 劳动权益和财产权益 D. 人身权益和婚姻家庭权益 我来回答: 提交
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