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问题 选择题

太阳系个行星几乎在同一平面内沿同一方向绕太阳做圆周运动，当地球恰好运行到某个行星和太阳之间，且三者几乎成一条直线的现象，天文学成为“行星冲日”据报道，2014年各行星冲日时间分别是：1月6日，木星冲日，4月9日火星冲日，6月11日土星冲日，8月29日，海王星冲日，10月8日，天王星冲日，已知地球轨道以外的行星绕太阳运动的轨道半径如下表所示，则下列判断正确的是：

 地球火星木星土星天王星海王星
轨道半径（AU）1.01.55.29.51930
A各点外行星每年都会出现冲日现象

B.在2015年内一定会出现木星冲日

C.天王星相邻两次的冲日的时间是土星的一半

D.地外行星中海王星相邻两次冲日间隔时间最短

答案

BD

题目分析：相邻两次行星冲日的时间间隔就是地球比该行星多运动一周的时间，根据开普勒第三定律可得根据万有引力提供向心力，周期，相邻两次行星冲日的时间间隔，即相邻两次行星冲日的时间间隔大于1年，所以选项A错，根据木星轨道半径是地球的5.2倍，木星周期大于11年，小于12年，所以木星冲日的时间间隔大于年小于1.1年，由于今年的冲日时间是1月6日，所以下次木星冲日在2015年，选项B对。由于木星相邻两次冲日的时间间隔的一半还不到一年，而所有行星冲日的相邻间隔都超过1年，所以天王星相邻两次的冲日的时间不可能是土星的一半，选项C错。根据海王星的轨道半径最大，周期最大，根据相邻两次冲日的时间间隔可判断海王星的时间间隔最短，选项D对。

单项选择题

人体能量的主要贮存形式是（）

A.脂肪

B.蛋白质

C.糖

D.氨基酸

E.维生素
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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.

"Pornographic" in Paragraph 3 probably means ______.

A．decent

B．instructional

C．sexual

D．commercial
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