I would have chosen all three of the lower ones. And I do not know about the first one. But I chose the second as the answer I think in most cases to be true.
I think that weak nerves is a continuum. A dog with very weak nerves, many symptoms, with bites, maybe the best thing for such a dog is to put it out of its pain.
I think most dogs do not fall into that extreme. And for those dogs, it is dependent on how weak their nerves are, what symptoms are showing, as to whether it will be mostly management with some improvement, or definite improvement, but of course management.
I think the dog is what it is. But by managing the environment, carefully socializing to new situations and people, building the confidence level of the dog and of the dog/owner team through training, the dog can be brought much farther than if the dog was put on a chain in the back yard and neither socialized or trained, and possibly allowing some negative experiences where the dog is as well. If you take that same dog and push it beyond its threshold and give it harsh corrections for any type of aggression, you can make a dog into a ticking time bomb.
I think the amount of improvement possible under ideal conditions is dependent on the dogs genes.
Heidi Ho, Odie
Joy-Joy, Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.