The ability _______ an idea is as important as the idea itself. (2011湖南)
A. expressing B. expressed
C. to express D. to be expressed
【知能进阶】常可用动词不定式作定语的情形有：
1. 当所修饰的词为desire, effort, failure, promise等时。
2. 当所修饰的名词前有the first/last/next, the only和the best, the most suitable等序数词或形容词最高级等修饰语时。
3. 当所修饰的名词与定语间有逻辑上的被动或主谓关系时。
