The ability _____ an idea is as important as the idea itself
A expressing B expressed C to express D to be expressed
The ability _____ an idea is as important as the idea itself
A expressing B expressed C to express D to be expressed
C
考查非谓语动词作定语的用法。句意为“想法重要，提出想法的能力也同样重要。”express 修饰的是ability, 为主动关系，排除B和D表示被动的选项；ability作为一个抽象名词，通常使用动词不定式做定语，联系到短语be able to do sth，不难推断正确选项为C。