Answer:
Complete predicate
Explanation:
A sentence may be divided into two broad parts: the subject and the predicate. The subject is the thing, animal or person that the sentence is about, and the predicate refers to the part that states something about the subject and any other information related to it, so it is the part that contains the verb and other phrases and objects.
In the sentence, "The graduation ceremony" is the event or thing that is being talked about, thus it is the subject; and the rest of the sentence: "lasted only two hours" is the complete predicate because it says something about the subject by containing the verb "lasted" and the phrase "only two hours."
