问题 选择题

在一个草原上,只有鹿和狼两种消费者,它们处于相对封闭的生态系统中,若人为地把狼灭绝,鹿群的变化将是( )

A      B      C      D

答案

题目分析:因为在生态系统中,某种动物与其他生物有着直接或间接的关系,当某种动物被灭杀后,会直接或间接地影响其他生物的生存,以致影响该动物所生存的整个生态系统.在该生态系统中存在:草→鹿→狼的食物链,全部捕杀狼群会使鹿的数量增加,从而使鹿场上的植物(鹿的食物)减少,以鹿为食动物也会随着鹿的增多而增多,后来鹿的数量会随着植物(鹿的食物)的减少而减少.

阅读理解

第三节:阅读理解(共15小题;每小题2分,满分30分)

(A)

JIUQUAN, Gansu Province, Sept. 6(Xinhua) ---- China’s manned spacecraft Shenzhou-7 will be launched at an appropriate time between Sept. 25 and 30 from the Jiuquan Satellite Launch Center in northwestern Gansu Province, a spokesman said here on Saturday. The mission will accomplish the first spacewalk by Chinese astronauts.

“All the major systems involved in the launching are now in the final preparation. The main tests for the spacecraft, the Long-March II-F rocket, suits for the space walk and a satellite accompanying the fly have also been finished, ” said the spokesman.

In addition, the ground control system is fully prepared, including the launch site, the landing site, and the communication for observation and control.

When Shenzhou-7 enters its orbit, one of the three taikonauts will conduct a space walk, said Zhao Changxi, a senior scientist with the project, earlier.

According to Zhao, cameras would be fixed outside and inside of the ship for live broadcasting of the space walk.

While the last mission of Shenzhou-6, with a crew of two, was aimed at several days of manned flight, this time the task might be more stringent as one of its main goals is the space walk.

Earlier reports said a crew of six astronauts had been chosen for the mission, with three manning the spacecraft and three substitutes. 

China successfully put two manned spacecrafts into orbit in 2003 and 2005 respectively, becoming the third country to send an astronaut into space after the United States and the former Soviet Union(now Russia).

56. What is the main idea of the passage?

A. Shenzhou-7 is better equipped than the last two spaceships.

B. Shenzhou-7 will be more successful than the last two launches.

C. All the systems involved in the launching have been prepared.

D. China is ready for the launching of Shenzhou-7.

57. We can learn from the passage ________.

A. This will be the third time for Chinese astronauts to have a space walk

B. Three of the six astronauts chosen for the mission will walk in space

C. The space walk will be live broadcasted on TV

D. Everything has been prepared except communication system

58. The underlined word”stringent”most probably means

A. challenging   B. encouraging   C. interesting   D. moving

单项选择题