The words are the following:
B. Fragment.
They are a sentence fragment, since there is no subject to be found. Who is sitting at the table? (No answer: no subject) A sentence needs a subject and a verb. The words at hand only have the latter. In other words, they lack a full sentence structure, which makes them incomplete to be called that.
If it were a sentence, it would look like the following example:
John is sitting right there at the table.
John: subject (Who is sitting at the table?/ Answer: John is.)
is sitting: main verb (to sit) conjugated in present continuous tense.
right there at the table: adverbial phrase of place (it does not belong to a basic sentence structure, that is, even if omitted, the sentence would still be a sentence).
