问题 单项选择题

在切除甲状腺10天后,物质代谢能力下降的老鼠的血液中,含量增加最多的激素是()

A.胰岛素

B.促甲状腺激素

C.生长素

D.甲状腺激素

答案

参考答案:B

解析:

切除甲状腺后,血浆中的甲状腺激素含量减少,通过反馈调节,使下丘脑和垂体分泌的激素促甲状腺激素释放激素和促甲状腺激素的含量增多,故B正确。

考点:本题主要考查激素分泌的调节,意在考查考生能理解所学知识的要点,把握知识间的内在联系,形成知识的网络结构的能力。

单项选择题

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.

Which of the following is NOT true about unwanted e-mail

A.It costs money to receive them.

B.It’s free to store them.

C.It takes time to access them.

D.It takes time to throw them away.

填空题