下列表示正确有______．（1）a⊆{a}；（2）{a}∈{a，b}；（3）{

如图所示，某轻绳一端固定一质量为m的小球，以另一端O为圆心，使小球在竖直平面内做半径为R的圆周运动，以下说法中正确的是（　　）

A．小球过最高点时，绳所受的弹力可以为零

B．小球过最高点时，最小速度为

C．小球过最高点时，最小速度为0

D．小球过最低点时，绳对球的作用力大小一定大于小球所受重力大小

The prospects for finding life beyond Earth may be brightening. Today, scientists are reporting evidence for yet another potential habitat in our solar system: Saturn’s moon Enceladus. Scientists mining new data from the Cassini spacecraft say they may have found evidence that Enceladus—the planet’s fourth-largest moon—hosts liquid water.
If the results hold up, this would bring to four the number of bodies in the solar system—including Earth—that display active volcanism. And since life as biologists know it requires liquid water and a source of energy, Enceladus would join Jupiter’s moon Europa and Saturn’s moon Titan, as well as Mars, as possible spots beyond Earth where simple forms of life may have gained or still maintain a foothold.
The discovery, however, is bittersweet for many scientists. NASA’s proposed budget for fiscal 2007 calls for a 50 percent cut in its astrobiology program. Although the program is a tiny piece of the agency’s overall spending plan for science, it’s a significant source of money for probing fundamental questions of how and why life emerged on Earth and whether life arose elsewhere in the universe.
A 50-percent cut "is almost a going-out-of-business-level cut" in a vibrant line of research that stands as one pillar supporting President Bush’s vision for space exploration, says planetary scientist Sean Solomon, who heads the Department of Terrestrial Magnetism at the Carnegie Institution of Washington.
Nevertheless, the research in today’s issue of the journal Science is the sort of thing that continues to light a fire under the field. Its report about liquid water under the icy surface of Enceladus is a "radical conclusion," acknowledges Carolyn Porco, who leads the imaging team working with data from the Cassini orbiter. But if the team is right, "we have significantly broadened the diversity of solar-system environments" that might have rolled out the welcome mat "for living organisms," she concludes. Images released last fall show the moon ejecting vast plumes of material near its unexpectedly warm south pole. As the team pondered the evidence, they nixed several explanations, including the idea that the particles in the plumes were driven by vapor billowing out as ice reached the surface and immediately turned into a gas. The last idea standing: Liquid water was venting from reservoirs near the surface, perhaps only tens of meters below the frigid crust. This explanation also helped solve the riddle of puzzlingly high levels of oxygen atoms found in Saturn’s neighborhood.
Confirmation could come with additional flybys. If water—and perhaps life—is present, it wouldn’t be "luxuriant," notes Jeffrey Kargel, a researcher at the University of Arizona at Tucson. It likely would face tough conditions—nasty chemicals, very low temperatures, and little energy to drive it. still, he adds, it’s premature to cross the moon off the list of possible "outposts" for life beyond Earth. Yet the prospect of building on these results could be dimmer with the threat of budget cuts. The proposed reductions post several challenges, researchers say.
One is the loss of important financial leverage. While money for experiments and other research related to astrobiology can come from other funding agencies, such as the National Science Foundation or even the National Institutes of Health, NASA’s program often provides the crucial missing piece that turns demanding and sometimes dangerous fieldwork into exciting results.
One of the biggest successes over the program’s 10-year history has been to help revolutionize the way science is done. Answering questions about the origins of life on Earth and the prospects for life elsewhere require p collaborations. From radio astronomers to biologists and geologists studying the evolution of Earth, groups are working together in ways they never thought of a decade ago, adds Edward Young, a geochemist at the University of California at Los Angeles.
"NASA’s made a lot of progress by making a relatively small investment in a way that has brought disparate experts together from the whole spectrum of physical and biological sciences. It’s a wonderful lesson on how to make progress by crossing these boundaries," Dr. Solomon says. "It would be regrettable to stop that experiment. \

According to the passage, one of the biggest successes over the program’s 10-year history is manifested by ______.

A．the advance in space probing technology

B．the p and smooth multi-disciplinary cooperation

C．the great progress with small investment

D．the discovery of life on some of the planets in the solar system

妨害公务罪：指以暴力威胁的方法，阻碍国家工作人员执行公务的行为。根据上述定义，下列行为属于妨害公务罪的是( )。

A．某公安人员骑车上街买东西时，与一人相撞，被撞者怒气冲冲，揪住公安人员不放，引起众人围观，严重影响了交通秩序
B．某检察院检察员小刘在侦查一起贪污案时，被该案嫌疑犯吴某的家属围攻、谩骂、殴打，并扬言若继续调查就将小刘家的房子砸烂
C．某公司会计叶某被告犯有贪污罪，检察人员到叶某公司查账，检察员杨某因为生气将一本账本的封页撕碎了，叶某公司的经理对此十分不满，与杨某争吵并收回了账本
D．胡某是一名个体户，因偷税而被罚款，为此胡某非常痛恨税务干部。一天胡某纠集了几个流氓，找到税务所干部董某家，将其家的门窗玻璃全部砸碎后扬长而去

试述小儿急性阑尾炎的特点。

人民法院在审理合同纠纷案件过程中，可以在双方当事人自愿的基础上进行调解，经调解达成协议的，制作调解书，调解书在（）生效。

A、经双方当事人签收后

B、送达之日

C、签收15日后

D、法院制作调解书之日