1. Being a child or an army officer: Fragment
Being a child or an army officer is a fragment because even though it's similar to a sentence in the sense that it begins with a capital letter, it is not a one since it does not convey a complete idea, therefore, in order to correct it, the fragment should be next to a main clause.
2. Mary has lived all of the world: Sentence
Mary has lived all of the world is a sentence because it has all the characteristics of one: it contains a subject (Mary) and a predicate (has lived all of the world) and it expresses a complete idea on its own.
