关于so as to 的用法到现在还不明白
大全91. Although one link in the chain was demonstrated to be weak, but not sufficiently so to require the recall of the automobile.
(D) demonstrably weak, it was not so weak as to require（D）
大全的解释是说so as to 只能用于系表结构，但似乎d 不是系表结构吧
先谢谢了 | 
