What do you understand by main document and data source

Read these lines from beowulf.often scyld scefing seized mead-benches from enemytroops, from many a clan, he terrified warriors, even thoughfirst he was found a waif, best explains why the author includes this information in theexposition? a. to emphasize that a hero must learn to be fierceb. to remember the famous story of a popular heroc. to express sadness about losing the old heroesd. to see whether people still respect the old heroes