She is supporting an inference from the text. An inference is something that is implied, and the person saying they've "witnessed much fighting" infers that they're old, whereas "I am wounded with iron" can be taken to mean he's been wounded by a weapon like a sword.
The third sentence. An abstract noun is a noun you can’t physically see or touch (examples of this are usually emotions like love, hate, excitement, etc). In the third sentence, opinion is a noun. You cannot see or touch an opinion.
