Which of the Following Is the Best Sentence to Include

Which of the following is the best sentence to include in the closing paragraph of a bad-news letter that turns down a job applicant?

A) Once again, we want to express how sorry we are that we are not able to offer you the position.
B) We wish you the best in your job search.
C) If you have further questions about this decision, please feel free to call me immediately.
D) We regret that we are unable to consider your application.