It’s difficult to tell when a fish fillet cooked en papillote is done because A. Fish fillets don’t change color
B. You can’t open the package to check
C. Fish dries out very quickly en papillote
D. Fillets are notoriously hard to cook

you have to tell us what you're talking about or it's impossible to answer.

it creates a visual picture of the man.

it conveys what the scene sounds like.

it describes the actions of the boy.

it reveals the poet’s opinion of the characters.

it encourages readers to care for the characters.

the answer is

we would need to be able to read the passage in question to determine which factor allowed david believe he could defeat goliath. post the passage, and i'd love to out.