Which one of the following types of writing is considered formal?

A. An instant message to a co-worker about after-hours plans

B. An invitation to an anniversary party

C. A personal email to a friend

D. A cover letter with a job application

D. i think its D because if youre going to apply for a job, A cover letter accompanies a CV. It's an opportunity to highlight what's in your CV and to provide real examples to support your ability to do the job. So it is the most formal of all answers.

D. You are having to communicate revolving around why you as a person should be in that position.