单选题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' of) 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.

单选题He had studied hard, he would have been able to pass the exam.

单选题John says that his present job does not provide him with enough ______ for his organizing ability.

单选题Everyone who has visited the city agrees that it is ______ with life.

单选题American Indian languages, which differ widely, tended to group many units of meaning into multisyllabic words.

单选题It is understandable that though adolescent maturational and developmental states occur in an orderly sequence, their timing ______ with regard to onset and duration.

单选题We will not be held responsible for any damage which results ________rough handling.

单选题My mother says a teaching machine has to be ______ to fit the mind of each boy and girl it teaches and that each kid has to be taught differently. A. modified B. considered C. adjusted D. remanufactured

单选题Some—such as liquid oxygen—are so cold that they Uembrittle/U many constructional materials and evaporate continuously if not refrigerated.

单选题Trial and error are the source of our knowledge.

单选题The feeling of competition among the students in all the classrooms where the test was going on was noticeable to everyone. A. discord B. discovery C. rivalry D. cooperation

单选题Because alcohol is a solvent, it is a component of many liquid medicines.

单选题According to the Bureau of the Census, what is an urban area?

单选题The streets of the Dual Springs neighborhood, a migrant-worker hub in northern Beijing, are ______ . That's no surprise; more than 13,000 people have been quarantined in China's capital to halt the insidious spread of severe acute respiratory syndrome (SARS). A. deserted B. vacated C. unlived in D. removed

单选题When he realized he had been suggested to sign the contract by intrigue, he threatened to start legal proceedings to cancel the agreement.

单选题He has made up his mind to relinquish all claim to the money.

单选题An overwhelming richness of vegetation may have caused the level of oxygen, to rise above today's ______ , with a corresponding depletion of carbon dioxide.

单选题Each year, in a never-ending cycle of death and rebirth , the rains sweep across southern Asia.

单选题{{U}}Virtually{{/U}} every theory has been concerned with either the structure or the function of the language.

单选题It seems that the president and the premier {{U}}like each other{{/U}} in many ways, and on many issues. A. resemble each other B. are identical with each other C. are similar to each other D. take to each other