关于1991年1月六级真题阅读理解的答案

1991年1月的英语六级真题中，阅读理解第一篇给出的参考答案为21-25 DAADC，而我做的答案是BDDBB，第一问问的是这篇文章主要讲什么，我选的是B救生工具的设计，答案给的是D救生工具的浮力，感觉不能接受这个答案，求高手指点，文章复制上来超过字数限制了，下面给出文章头两句方便高手搜索。

Merchant and passenger ships are generally required to have a life preserver for every person aboard and, in many cases, a certain percentage of smaller sizes for children. According to United States Coast Guard requirements, life preservers must be simple in design, reversible, capable of being quickly adjusted to fit the uninitiated individual, and must be so designed as to support the wearer in the water in an upright or slightly backward position.

这么老的题目了还做？你看看他答案为什么这么说呗，看看文章讨论的范围是不是没有包含“设计”的全部内容，太笼统。