Answer:
Prehistoric people could not record history, for they had not invented writing.
Explanation:
Compound sentences are sentences that consist of at least two independent clauses connected by a semicolon or a coordinating conjunction preceded by a comma.
Independent clauses are clauses that can stand alone as a sentence. This means that they contain all elements a sentence should contain (a subject and predicate) and express a complete thought.
The given compound sentence consists of two independent clauses connected by the conjunction for:
In case you need to identify the subjects and predicates as well, I've pointed them out. The subjects are underlined, and the predicates are written in bold letters.