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It can be inferred from the passage that ______.
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

A.A.vanillin
B.not
C.in
D.synthesized

【参考答案】

B
解析：推断题型。见第三段第一句：Many of the chemical compounds…and are......

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Electronic mail has become an extremely important and popular means of communication.The convenience and efficiency of electronic mail are threatened by the extremely rapid growth in the volume of unsolicited commercial electronic mail. Unsolicited commercial electronic mail is currently estimated to account for over half of all electronic mail traffic, up from an estimated 7 percent in 2001, and the volume continues to risE.Most of these messages are fraudulent or deceptive in one or more respects.The receipt of unsolicited commercial electronic mail may result in costs to recipients who cannot refuse to accept such mail and who incur costs for the storage of such mail, or for the time spent accessing, reviewing, and discarding such mail, or for both. The receipt of a large number of unwanted messages also decreases the convenience of electronic mail and creates a risk that wanted electronic mail messages, both commercial and noncommercial, will be lost, overlooked, or discarded amidst the larger volume of unwanted messages, thus reducing the reliability and usefulness of electronic mail to the recipient. Some commercial electronic mail contains material that many recipients may consider vulgar or pornographic in naturE.The growth in unsolicited commercial electronic mail imposes significant monetary costs on providers of Internet access services, businesses, and educational and nonprofit institutions that carry and receive such mail, as there is a finite volume of mail that such providers, businesses, and institutions can handle without further investment in infrastructurE.Many senders of unsolicited commercial electronic mail purposefully disguise the source of such mail.Many senders of unsolicited commercial electronic mail purposefully include misleading information in the messages' subject lines in order to induce the recipients to view the messages. While some senders of commercial electronic mail messages provide simple and reliable ways for recipients to reject (or 'opt-out' o0 receipt of commercial electronic mail from such senders in the future, other senders provide no such 'opt-out' mechanism, or refuse to honor the requests of recipients not to receive electronic mail from such senders in the future, or both.Many senders of bulk unsolicited commercial electronic mail use computer programs to gather large numbers of electronic mail addresses on an automated basis from Internet websites or online services where users must post their addresses in order to make full use of the website or servicE.The problems associated with the rapid growth and abuse of unsolicited commercial electronic mail cannot be solved by the government alonE.The development and adoption of technological approaches and the pursuit of cooperative efforts with other countries will be necessary as well.According to the passage, efficiency of e-mail is threatened by ______.A.heavy e-mail trafficB.fraudulent e-mail messagesC.large volume of messagesD.increasing amount of unwanted e-mail
A.B.
C.
D.
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F.
G.
According
H.
A.heavy
I.fraudulent
J.large
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LandfillsYou have just finished your meal at a fast food restaurant and you throw your uneaten food, food wrappers, drink cups, utensils and napkins into the trash can. You don't think about that waste again. On trash pickup day in your neighborhood, you push your can out to the curb, and workers dump the contents into a big truck and haul it away. You don't have to think about that waste again, either. But maybe you have wondered, as you watch the trash truck pull away, just where that garbage ends up.Americans generate trash at an astonishing rate of four pounds per day per person, which translates to 600.000 tons per day or 210 million tons per year! This is almost twice as much trash per person as most other major countries. What happens to this trash? Some gets recycled (回收利用) or recovered and some is burned, but the majority is buried in landfills.How Much Trash Is Generated?Of the 210 million tons of trash, or solid waste, generated in the United States annually, about 56 million tons, or 27 percent, is either recycled (glass, paper products, plastic, metals) or composted (做成堆肥) (yard waste). The remaining trash, which is mostly unrecyclable, is discardeD.How Is Trash Disposed of?The trash production in the United States has almost tripled since 1960. This trash is handled in various ways. About 27 percent of the trash is recycled or composted, 16 percent is burned and 57 percent is buried in landfills. The amount of trash buried in landfills has doubled since 1960. The United States ranks somewhere in the middle of the major countries (United Kingdom, Canada, Germany, France and Japan) in landfill disposal. The United Kingdom ranks highest, burying about 90 percent of its solid waste in landfills.What Is a Landfill?There are two ways to bury trash:Dump--an open hole in the ground where trash is buried and that is full of various animals (rats, mice, birds). (This is most people's idea of a landfill!)Landfill--carefully designed structure built into or on top of the ground in which trash is isolated from the surrounding environment (groundwater, air, rain). This isolation is accomplished with a bottom liner and daily covering of soil.Sanitary landfill--landfill that uses a clay liner to isolate the trash from the environmentMunicipal solid waste (MSW) landfill—landfill that uses a synthetic (plastic) liner to isolate the trash from the environment.The purpose of a landfill is to bury the trash in such a way that it will be isolated from groundwater, will be kept dry and will not be in contact with air. Under these conditions, trash will not decompose (腐烂) much. A landfill is not like a compost pile, where the purpose is to bury trash in such a way that it will decompose quickly.Proposing the LandfillFor a landfill to be built, the operators have to make sure that they follow certain steps. In most parts of the world, there are regulations that govern where a landfill can be placed and how it can operatE.The whole process begins with someone proposing the landfill.In the United States, taking care of trash and building landfills are local government responsibilities. Before a city or other authority can build a landfill, an environmental impact study must be done on the proposed site to determine:the area of land necessary for the landfillthe composition of the underlying soil and bedrockthe flow of surface water over the sitethe impact of the proposed landfill on the local environment and wildlifethe historical value of the proposed siteBuilding the LandfillOnce the environmental impact study is complete, the permits are granted and the funds have been raised, then construction begins. First, access roads to the landA.YB.NC.NG
A.B.000
C.
How
D.
How
E.
What
F.
G.
H.
Proposing
I.
J.Y
B.N
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