分层抽样按比例分配各层样本量是（）。 A.与N成比例分配 B.与Y成比例分配 C.与

Space travel is nothing new. The first spacecraft with a human was sent up into space in 1961. Since then, people have not only traveled to space, but also many of them have lived there in space stations for some time.

The Soviet Union(前苏联) sent the first space station into space in 1971. This space station was called Salyut 1. Salyut 1 was designed as a place where people could live while they observed space and did experiments. The first group of astronauts lived there for 23 days. The Soviet Union went on to make seven more Salyut space stations. At about the same time, the United States built its own space station, called Skylab.

Astronauts visited and often lived in these space stations for a short time. However, it wasn’t until the late 1980s when The Soviet Union sent the Mir space station that people began to live in space for a longer time. Mir stayed in space from 1989 until 2001, when it was decided that the space station was too old and no longer safe to live in.

Living in space stations seems to be fun, but astronauts face many problems. One of them is food. All the meals on space station are put together on Earth and sent there by space shuttle. Because the food has to last a long time (sometimes up to three months), a lot of it has to be stored in cans. The space station does not have a fridge, but it has a cool room to keep fruit and vegetables fresh. Astronauts also eat many other foods such as dried meat that do not need special care.

Without the help of gravity, sitting down to eat can be tough. Astronauts sometimes have to fix themselves to the wall while eating. They also have to be very careful to that food does not float away.

小题1:Which of the following has the closest meaning to the underlined word “observed” in Paragraph 2?

A．Discovered

B．Checked

C．Watched

D．Fixed小题2: What can we infer(推断)from the passage?

A．Astronauts can never have a chance to eat fresh food when they live in space station.

B．The Soviet Union sent a total of 9 space stations into space in the 1970s and 1980s.

C．Astronauts could live in the Mir space station for no more than three weeks.

D．Space travel has quite a long history of more than 60 years.小题3:What is the best title of this passage?

A．Exploring Space

B．Space Travel

C．Living in Space

D．Space Stations

对放、化疗均高度敏感的肿瘤为（）

A.骨肉瘤

B.鳞状细胞癌

C.恶性淋巴瘤

D.纤维肉瘤

E.鼻咽癌

如图所示有理想边界的两个匀强磁场，磁感应强度均为B=0.5T，两边界间距s=0.1m，一边长L=0.2m的正方形线框abcd由粗细均匀的电阻丝围成，总电阻为R=0.4Ω，现使线框以v=2m/s的速度从位置Ⅰ匀速运动到位置Ⅱ，则下列能正确反映整个过程中线框a、b两点间的电势差U_ab随时间t变化的图线是（　　）

A．

B．

C．

D．

It’s not that we are afraid of seeing him stumble, of scribbling a mustache over his career. Sure, the nice part of us wants Mike to know we appreciate him, that he still reigns, at least in our memory. The truth, though, is that we don’t want him to come back because even for Michael Jordan, this would be an act of hubris so monumental as to make his trademark confidence twist into conceit. We don’t want him back on the court because no one likes a show-off. The stumbling That will be fun. But we are nice people, we Americans, with 225 years of optimism at our backs. Days ago when M.J. said he had made a decision about returning to the NBA in September, we got excited. He had said the day before, "I look forward to playing, and hopefully I can get to that point where I can make that decision. It’s O.K. to have some doubt, and it’s O.K. to have some nervousness." A Time/CNN poll last week has Americans, 2 to 1, saying they would like him on the court ASAP. And only 21 percent thought that if he came back and just completely bombed, it would damage his legend. In fact only 28 percent think athletes should retire at their peak. Sources close to him tell Time that when Jordan first talked about a comeback with the Washington Wizards, the team Jordan co-owns and would play for, some of his trusted advisers privately tried to discourage him. "But they say if they try to stop him, it will only firm up his resolve," says an NBA source. The problem with Jordan’s return is not only that he can’t possibly live up to the storybook ending he gave up in 1998—earning his sixth ring with a last-second championship-winning shot. The problem is that the motives for coming back—needing the attention, needing to play even when his 38-year-old body does not—violate the very myth of Jordan, the myth of absolute control. Babe Ruth, the 20th century’s first star, was a gust of fat bravado and drunken talent, while Jordan ended the century by proving the elegance of resolve; Babe’s pointing to the bleachers replaced by the charm of a backpedaling shoulder shrug. Jordan symbolized success by not sullying his brand with his politics, his opinion or superstar personality. To be a Jordan fan was to be a fan of classiness and confidence. To come back when he knows that playing for Wizards won’t get him anywhere near the second round of the play-offs, when he knows that he won’t be the league scoring leader, that’s a loss of control. Jordan does not care what we think. Friends say that he takes articles that tell him not to come back and tacks them all on his refrigerator as inspiration. So why bother writing something telling him not to come back He is still Michael Jordan.

将50公斤的人提升10公斤需要的能量是（）。

A.5千万焦耳

B.一千万焦耳

C.5百万焦耳

D.一百万焦耳