问题 单项选择题

  多少年来,人们一直在幻想研制一种航空航天运输工具,它既能从机场跑道起飞,又能以高超音速穿越大气层进入宇宙空间,完成航天任务后再入大气层,在机场水平着陆,而经过简单维修后,短期内又能重上蓝天,重复使用几十几百次,这类既具有高超音速运输机功能又具有天地往返运输系统功能的重复使用有翼飞行器,被称之为航空航天飞机,简称空天飞机。它是一种新型运输工具,具有一般飞机和航天器所没有的优越性。首先,与普通运输客机相比,它能够以更高速度在大气层上层(或近宇宙空间)机动飞行,从而大大缩短远距离运输的时间,如德国桑格尔空天飞机(第一级改进型)由法兰克福经洛杉矶飞至东京仅需3小时15分钟,美国“东方快车”由华盛顿飞至东京仅需2小时,而由欧洲飞至澳大利亚仅需1小时。再者,与以往的一次性使用飞船和多次部分重复使用航天飞机相比,它在重复使用性、机场水平起降能力,利用大气层能源、灵活机动性、发射操作费用、可维修性和复飞间隔时间等方面均有大幅度改进。如其重复使用次数可增至50至数百次,发射(运输)费用仅相当于运载火箭发射费用的三分之一(甚至十分之一或二十分之一),大型航天飞机发射费用的五分之一,比起用火箭发射小型航天飞机的费用也要降低10-30%。再如复飞间隔时间,空天飞机一般在着陆后数小时或略长时间内即可重新起飞。这是航天飞机所无法做到的。因此,空天飞机有着十分广阔的发展与应用前景,不仅可以进行全球性的高超音速运输,而且可以完成各项成本较低、效益较高的航天运输使命,为空间站往返运输人员和货物,执行各种航天军事任务。展望21世纪,它必然会成为遨游于大气层与宇宙空间的骄子。

空天飞机是指()。

A.兼具飞机与火箭功能的运输工具

B.能从机场起飞,穿越大气层进入宇宙空间的运输工具

C.具有高超音速运输机功能,又具有天地往返运输系统功能的重复使用有翼飞行器

D.是航天飞机的一种,使用费用较低

答案

参考答案:C

单项选择题 A型题
填空题

Although no longer slavers after the Civil War, American blacks took no significant part in the life of white America except as servants or laborers. Many thousands of them emigrated from the war-ravaged South to the North from 1865 to 1915 in the hope of finding work in the big industrial cities. Whole communities of blacks crowded together into ghettos in New York City, Chicago and Detroit, where once the poor white immigrants had lived. These ghettos, neglected by the city authorities, became slums. The schools to which black children went were hopelessly inadequate. Unemployment in black ghettos remained consistently higher than in white communities.

41. Serious problems with black ghettos.__________

Stable family life was difficult to maintain.

42. The extreme poverty of the blacks. __________

In the late 1970s, nearly a third of all blacks still belonged to the so-called "underclass", they are so "under-privileged" and poor that they cannot seize the opportunity for advancement.

43. Efforts to put an end to racial discrimination. __________

Race relations in the USA continue to be a thorny problem.

44. Improvements in lives of the blacks. __________

Despite some setbacks, race relations are improving.

45. Prevailing violence in solving racial problems. __________

It is said that television had an enormous influence on frustrated and bitter blacks, for it showed them bow much better whites on the whole lived than blacks. At the end of the 1960s, there were serious riots in many cities.

The violence quickly died down. Blacks began to use their votes to exert political pressure. Cities like Atlanta (Georgia), Gary (Indiana), and Los Angeles (California) elected black mayors. Integration of schools, despite resistance from white groups, goes on, and the proportion of blacks in American colleges has increased dramatically in the last 20 years. There are reasons to maintain a cautious optimism that progress in race relations will continue.

[A] It has been estimated that there are more than 20 million Americans in this category, 10% of the population, including many millions of whites.

[B] Blacks are gaining in self-confidence. In more and more areas they are winning control of their communities, and their standard of living is going up faster than that of the poor whites. It is still a hard struggle. There is still prejudice and even some hatred, but in most walks of American life there are now more blacks than ever before.

[C] The era of blatant discrimination ended in the 1960s through the courageous actions of thousands of blacks participating in peaceful marches and sitins, to force Southern states to implement the Federal desegregation laws in schools and public accommodations. Down came the "whites only" notices in bused, hotels, trains, restaurants, sporting events, restrooms and on park benches that once could be found everywhere throughout the South. Gone were the restrictions that prevented blacks voting. Gone, too, were the hideous lynch-ings, which since the Civil War had caused the death of thousands of innocent blacks— hanged without trial by white mobs. However, even today, poor, uneducated lacks do not always receive the same degree of justice that the more affluent and better educated can expect.

[D] Many blacks chose to keep silent about their unfairness instead of resorting to violence. But their silence was also problem provoking: on the one hand, silence would build up a lot of complaints and hatred in their minds, thus resulting in a negative approach to life and everything; on the other hand, silence would give the whites an impression that the blacks take the reality for granted and put more racial discrimination on them.

[E] Unemployed fathers would on occasion walk out of their homes and never return. Children neglected by their parents turned in some instances to drugs and crimes. There are more than 700 murders a year in cities like New York, Detroit, Los Angeles and Houston, and most of these deaths are of blacks killed by blacks. The black ghettos are dangerous both for blacks and non-blacks.

[F] Radical blacks like the Black Panthers demanded a free black state within the Union, and advocated violence to achieve that end and to protect themselves against what they felt was police brutality toward blacks. For a while, violence overshadowed the influence of the greatly respected pacifist black, Martin Luther King, Jr. , who had provided the inspiration and leadership for those devoted to a peaceful change and whose murder in 1968 stunned America.

44()