问题 判断题

调制解调器负责把计算机数字信号进行放大和整形。

答案

参考答案:

阅读理解与欣赏

祖冲之 

       祖冲之是我国南北朝时期一位杰出的科学家。他学习古代著作,但从不盲从古人。他独立思考,敢于大胆怀疑、提出问题。因此他在学习前人的同时,超过前人,登上了当时科 学的顶峰。    

       祖冲之在学术上有很大的贡献。在数学方面,他把圆周率推算到小数点后第七位,这不仅远远地超过了我国古人,而且比欧洲科学家取得相同的成果早了一千来年。      

       在天文学方面,祖冲之的贡献也很大。历来的天文学家,把一年四季变化的规律,看得比较机械呆板。祖冲之根据自己对天文变化的准确计算,认为别人认定的规律,实际上每年要差一点,因此,他不同意别人用闰月的计算法。祖冲之根据他的理论,写出新的历法书,叫“大明历”,并把它推荐给国家采用。当时有个人叫戴法兰,坚决反对这样做。他盲目迷信古人,认为历法是祖宗制定的,万世不可变。戴法兰的官大,好多人怕他,都附和他。 祖冲之说:“古人对的应当相信,错的应该改正,盲目地信古疑今,是错误的。”他坚持自己的主张,虽然他的历法当时没有被采用,但十年后,“大明历”的先进之处越来越被人们理解,国家最终还是废除了旧历法,采用了“大明历”。   

       祖冲之还是一位能工巧匠。他制成了指南车,发明了千里船,只可惜这些精巧的器械, 都没有流传下来。

1.短文共有           自然段,分别概述了祖冲之在           和          等方面的成就。

2.本文的中心句是___                                                                             _ 。 

3.祖冲之对待科学的态度是怎样的?

                                                                                                                       

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.

"Disguise" in Paragraph 4 is closest in meaning to ______.

A. reveal
B. hide
C. deliver
D. post