GMAT Sentence Correction (SC) | The gyrfalcon, an Arctic bird of prey, has survived a close

I am still not very clear for why A should use "greater" vs "more". Can someone help? I read all the prior posts but still a little confused. Why? If I see this issue again, I am not sure if I would be able to pick the correct answer.


Split1) Pronoun issue. Gyrfalcon = singular, they = plural. Cannot go together. C and D are out.

Split2) Idiom "greater than" vs "more than". If you want to make a comparison, use "greater than". I believe Split2)