为了提高广大学生的英语水平，提高英语专业学生的专四通过率，特提供以下英语长难句，供大家练习参考：
56. Supporters of the Star Wars defense system hope that this would not only protect a nation against an actual nuclear attack, but would be enough of a threat to keep a nuclear war from ever happening.
57. Neither would it prevent cruise missiles or bombers, whose flights are within the Earth’s atmosphere, from hitting their targets.
58. Civil rights activists have long argued that one of the principal reasons why Blacks, Hispanics, and other minority groups have difficulty establishing themselves in business is that they lack access to the sizable orders and subcontracts that are generated by large companies.
59. During the nineteenth century, she argues, the concept of the “useful” child who contributed to the family economy gave way gradually to the present day notion of the “useless” child who, though producing no income for, and indeed extremely costly to its parents, is yet considered emotionally “ priceless”.
60. Well established among segments of the middle and upper classes by the mid-1800’s, this new view of childhood spread throughout society in the late nineteenth and early twentieth centuries as reformers introduced child labor regulations and compulsory education laws predicted in part on the assumption that a child’s emotional value made child labor taboo.
56、星球大战防御系统的支持者们希望它不仅能保护一个遭受核攻击的国家，也希望它能成为使核攻击永不发生的足够威胁。
57、它也不能防止轨道在地球大气层以内的洲际导弹和轰炸机命中目标。
58、人民活动家一直认为黑人和拉丁美人难以在生意上立足的原因是因为他们难以取得大公司的大宗定单和分包合同。
59、她认为十九世纪给家庭经济作出贡献的孩子才“有用”的概念慢慢改变了，今天提到那些没有挣取收入的“无用”孩子，甚至还要花销很多，仍然在情感上被认为是无价的。
60、这种关于孩子的观点到19世纪时已在中上阶级中建立，并于19世纪末20世纪初在社会上广泛传播，当时改革者们推行童工规定和义务教育法，部分来源于孩子的情感价值的假设，这都使得使用童工被禁止了。