C it has established itself as a supreme adapter in an era when to be able
D it has established itself as being a supreme adapter in an era when its ability
E it has established itself as a supreme adapter in an era when the ability
问题在于C和E, C中 when to be able......和 E的 when the ability to.....为什么C不行呢 不定式不是也能作主语吗 麻烦大家来解救一下我。。。。