今天在百度汉英大字典上看到个句子Coulditbesaidthatitisimpossibleofattainment?
我查了下字典也没be impossible of如此的固定搭配。老师这里为何用of呢
itisimpossibleofattainment = it is impossible to attain
通过剖析以下COCA类似例句，大家可以得知形容词impossible的一个使用方法，即：
Sth is impossible of + 表示动作意义的抽象名词 = Sth is impossible to do (悬空不定式）。比如：
Actions of animals areimpossibleofexplanation as due to instinct.
= Actions of animals areimpossibletoexplain as due to instinct.
Any ethical goal that is conceptuallyimpossibleofachievement is an absurd goal.
= Any ethical goal that is conceptuallyimpossibletoachieve is an absurd goal.
在以上二个句义相等的结构中，悬空不定式或者of介词短语都是表语形容词impossible的不足语。
以下为COCA部分类似例句：
At first Fox was pessimistic, considering the Serra asimpossibleofconquest by a locomotive as the Himalayas.
Or the problem may be so specialized and varying in nature as to beimpossibleofcapture within the boundaries of a general rule.
This intellectualizing is perhaps akin to this authors going far afield in his verbose analysis, something like schizophrenic word-salad : Nearlyimpossibleof
comprehension.
After the instances I have cited of actions of animals which areimpossibleofexplanation as due to instinct, Mr. Burroughs may reply: Your instances are easily explained by the simple law of association.
...it is somethingimpossibleofdescribe.
Surely any ethical goal that is conceptuallyimpossibleofachievement is an absurd goal.
