1--5 BCDCA
1.根据文章中第一自然段，第三、四句话：To find out what was happening they stopped their work to check some parts of the computers. To their horror, they found out that most of their stored information was got rid of by computer viruses (病毒). 可以找到正确答案。
2.第二段中第三句 “They created the viruses just to show their intelligence” 表明了他们制造病毒的目的是为了显示智商高，B选项理解为测试能力，这与文中内容有出入。
3.文章最后一句说明如何除去病毒仍是问题，这就证明病毒难以除去。B选项和C选项文中没有提及。
4.根据文章中第二自然段最后一句话： When the time comes they will attack the computers by lowering the important functions, damaging their normal programs or even getting rid of a great deal of information which operators of the computers often use or store, what’s worse, it still can reproduce itself in great quantities within a short time.可知最佳答案为C。
5.文中只在第二段中提到该病毒可在电脑中潜伏一段时间才发作并复制，并未提到将向其他电脑扩散，所以B不正确。最后一段落中提到了四个受到病毒攻击的国家名称，但这并不表示只有四个国家受到电脑病毒攻击，所以C太狭隘。