—Must I come back before supper, mum? —N

超声图像上区别肝静脉和门静脉的最好方法是（）。

A.门静脉管壁较厚

B.肝静脉管径较粗

C.门静脉分支较少

D.追踪它们的起源处

E.肝静脉随呼吸搏动

已知地球表面附近的重力加速度为g，地球的半径为R，则地球的第一宇宙速度为（用字母表述）______； 地球第一宇宙速度的大小为（具体数值）______km/s．第二宇宙速度的大小为（具体数值）______km/s．

选出下边不是对偶句的一项：(　　)

　　A北通巫峡，南极潇湘 　　　B朝晖夕阴，气象万千

　　C衔远山，吞长江 　　　　　D日星隐耀，山岳潜形

E

A United Nations report says the number of people in the world is expected to reach 6500 million this July. By the middle of the century, the population could reach more than 9000 million. That would be an increase of 40﹪.

These numbers are fresh estimates for a report on world population change from 1950 to 2050. Hania Zlotnik is director of the U.N. Population Division. She says the world has added nearly 500 million people in the last six years.

But, in her words, "the good news is that new estimates show that it will take a little longer" to add the next 500 million. Mizz Zlotnik says this will probably happen by 2013.

The U.N. report says most population growth by 2050 will take place in less developed countries. Their population is expected to increase from 5000 million today to almost 8000 million. The population of more developed nations is expected to stay about the same, at just over 1000 million.

The report says nine countries will be responsible for about half the world population increase by 2050. These include Bangladesh, China, the Democratic Republic of Congo, Ethiopia and India. The others are Nigeria, Pakistan, Uganda and the United States.

Twelve countries are expected to have populations at least three times the size now. These include Afghanistan, Burkina Faso, Burundi, Chad, Congo and the Democratic Republic of Congo, and East Timor. The others are Guinea-Bissau, Liberia, Mali, Niger and Uganda.

The report says birth rates remain low in forty-four developed countries.

Today, worldwide, there is an average of two-point-six children per woman. This number is expected to fall to just over two children per woman in  2050. But U.N. population experts note that they cannot be sure which way birth rates will go in the future.

The U.N. report also notes that AIDS has increased death rates and slowed population growth in sixty countries. The area most affected by the disease is Southern Africa.

There, how long people live has fallen from an average of sixty-two years in 1995 to forty-eight now. Researchers believe life expectancy will fall to forty-three years by 2015, then begin a slow recovery.

67. Which of the following statements is true?

A. The population growth will slow down in the next few years.

B. Most population growth will take place in developed countries.

C. There is an average of 2.6 children per woman in developed countries.

D. The area most affected by AIDS is Uganda.

68. Which one is the best title of this passage?

A. AIDS slowed population growth.

B. Most population growth will take place in less developed countries.

C. Population growth and death rate.

D. UN world population report.

69．The author believes that the population growth results from_______

A. The birth rate in developed countries is too high.

B. The birth rate in developing countries is too high.

C. AIDS hit only a few countries.

D. A decrease in death rate.

70. Which of the following best describe the author’s attitude towards the rapid population growth?

A. sympathetic     B. happy       C. optimistic     D. critical

小型露天采石场爆破作业，应按批准的爆破设计书或（）进行。

A、领导指示

B、爆破说明书

C、任务时间