The ivory-billed woodpecker, once the largest woodpecker in North America at a striking 20 inches tall, has moved in and out of the extinct category, with scientists consistently unable to find solid proof for the bird to still exist.
for the bird to still exist
for the bird as still existing
for the bird's continued existence
that the bird still exists
of the bird and its continued existence
The only real error in choice C is "proof for...", as you noticed. It's not decidedly more wordy than the correct version.
登录 或 注册 后可以参加讨论