A subject complement is a word that describes the subject of a sentence that follows immediately after a linking verb. Like the name suggests, it complements the subject. It can either be a noun, adjective or pronoun.
Therefore, the subject complement from the sentence "Bret Hartes' poems and prose were often considered witty" is "often considered witty".
okay, so biascally you just have to rewright what you have written in the introduction and the body but in a different way. it's like you are revising to the reader.