Answer now. "correctly."

what is the purpose of a persuasive letter?

to demonstrate the steps in a process
to inform readers about meaningful research
to convince readers to take action or support a cause
to explain a societal problem that needs to be addressed

To convince readers to take action or support a cause

Explanation: The verb to persuade (from which the adjective persuasive comes) means to cause someone to do a specific action or believe in a certain idea through the use of reasoning, presenting logical arguments; demonstration, explanation and information may be part of the persuasive strategy, but those are not the main purpose of a persuasive letter.

explanation:

the silver bells of the sleds are merry and keep time in the winter nights while the sky twinkles happily. the golden bells of weddings are delightful in their peaceful happiness, foretelling a rapturous future. meanwhile, the brazen alarm bells scream frightfully in the night, with a discordant and desperate sound. in their clamor, these bells convey terror, horror, and anger. finally, the iron bells are solemn and melancholy, while those in the church steeple are like ghouls who feel happiness. the king of the ghouls, who rings the bells, cheerfully keeps time with the moaning and groaning bells.