You didn't italicize anything. However, I can assume that <em>a three-act farce </em>is italicized, and if that is the case, then this is an appositive phrase.
"A three-act farce" is an appositive. It is not a clause as it lacks a verb.
An appositive is a noun or noun phrase that renames another noun right beside it. The appositive can be a short or long combination of words. The appositive tends to be placed between commas. In this particular case, "A three-act farce" is renaming the noun mentioned before: the PLAY. And it is separated from the rest of the sentence with commas.
The correct answer for the question that is being presented above is this one: "c. Five." A student researcher should consult at least five varied sources for an 800- to 1,000-word research paper. It has to make sure that everything is okay and perfect.
