Which of the Following Would Be Good Advice to Follow

Which of the following would be good advice to follow when writing a claim-denial letter?

A) Address your message To whom it may concern to keep the message objective and impersonal.
B) Make sure that the customer knows what he or she has done incorrectly, so they won't make the same mistake again.
C) Avoid you statements that sound preachy.
D) Remind the customer that you are aware that most claims are fraudulent.