D. the applicant's contact information and a request for an interview:
Step-by-step explanation:
A. facts about yourself that would interest the reader: This should come in the initial part to impress the reader.
B. specifics as to why the employer should take the application process further with an interview: This is the most important paragraph and should come in the middle of the letter.
C. the signature: This is the last part of the letter to acknowledge that he/applicant has written it.
D. the applicant's contact information and a request for an interview: This is the right answer. Final para should quote the request and contact information so that there is a chance of applicant getting short-listed and possibility of getting a call back.