Which of the Following Guidelines Need to Be Followed While

Which of the following guidelines need to be followed while choosing a level of formality for a document?

A) Using a formal style even if the document is for someone the writer has interacted with
B) Using contractions if the document is for someone the writer is not familiar with
C) Avoid using abbreviations in e-mails if they are part of a group's culture
D) Paying particular attention to one's style of writing when conveying bad news
E) Using personal pronouns and second-person in reports to make it more efficient