The fragment that is made up of a complete predicate is option A. "could not be heard above the voices in the hallway"
In grammar, the predicate is defined as the part of the sentence that contains the verb and gives information about the subject.
Option A is the only option that contains a verb, in this case "could" and it is providing information about a subject we don´t know. The only options lack verbs,
For the introductory paragraph, you should start by introducing broad ideas about the subject at hand. In this particular case, it would be a good idea to provide some background information about Sonia Nazario and maybe a little bit of information about his biographies and editorials. Nothing in your introductory paragraph should compare or contrast the two at all...you should save this for your body paragraphs. Make sure your thesis statement is the very last sentence of your introductory paragraph...this is the most important thing when it comes to most English teachers.
Answer is that’s to much reading