分析柱式桥墩和桩柱式桥墩为何在桥梁中得到较广泛的采用？

On the afternoon of September27, 2008, Astronaut Zhai Zhigang became the first Chinese man to walk in space on Saturday, clambering（爬上,攀登） out of China's Shenzhou VII space craft in a technological feat（成就，功绩）that made the Chinese people excited.

"I'm feeling quite well. I greet the Chinese people and the people of the world," Zhai said as he climbed out of the craft at around 16:40 Beijing time, a historic achievement telecast live on CCTV. Tens of millions of Chinese viewers gathered before TV screens to watch the moment.
Chinese President Hu Jintao and other top leaders had appeared at the Beijing Aerospace Control Center to watch the live transmission of Zhai's spacewalk.
Zhai, 42, chosen by an expert team for the first "out-of-capsule activity," showed a red national flag, helped by colleague Liu Boming, who also briefly popped his head out of the capsule.
Zhai slowly made his way towards a test sample of solid lubricant（润滑剂）outside the capsule, took a sample and handed it to Liu.
Zhai safely returned inside the craft after about 20 minutes. The walk marked the highpoint of China's third manned space journey, which has received widespread media coverage.
Zhai wore a $4.4 million Chinese-made suit weighing 120-kg. Liu wore a Russian-made one and acted as an assistant.
The third crew member, Jing Haipeng, monitored the ship from inside the re-entry module. w.w
The risky maneuver is a step towards China's longer-term goal of building a space lab and then a larger space station, analysts said.
"On this flight, Chinese people's footprints will be left in space for the first time," said a commentary（评论）by the Xinhua news agency.
The astronauts went aboard on their walk after receiving a clean bill of health from doctors on the ground at mission control in Beijing, Xinhua said.
Zhai's suit has 10 layers and takes up to 15 hours to assemble and put on.
China's first manned spaceflight was in 2003. A second, two-manned flight followed in 2005. The only other countries that have sent people into space are Russia and the United States.
Shenzhou VII took off on Thursday and is due to land on the northern steppes(草原) of Inner Mongolia on Sunday.
小题1:The space walk done by the Chinese astronaut was historic because ______.

A．it was telecast live	B．there were more Chinese viewers than ever
C．it was the first space walk carried out by Chinese astronauts
D．top leaders watched the space walk

小题2: The following statements are true except ______.

A．The lubricant put outside the capsule was a test sample

B．It took Zhai Zhigang about 20 minutes to return to the craft safely

C．Many televisions and newspapers around the world reported the event

D．There is an aerospace control center in the capital

小题3:The significance of the space walk is ______.

A．that the astronaut can work outside the spacecraft

B．it marks a successful step towards China’s longer-term goal of building a space lab as well as a space station

C．it has attracted tens of millions of people to watch the walk

D．that the Chinese-made space suit can be used in space

小题4:What does the underlined word “clean” mean in the passage?

A．healthy

B．paid-off

C．not dirty

D．clear

小题5: The best title of the passage is ______.

A．First Footprints of Chinese People in Space

B．Expensive Space Suit

C．Three Successful Manned Flights by Chinese Astronauts

D．Historic Space Walk by Chinese Astronaut