If You Are Offered a Job You Decide Not to Accept

If you are offered a job you decide not to accept, what is the best action to take?

A) Call or write a note declining the offer but thanking the employer for their time and the offer.
B) Call or write to explain to the employer why you are turning down the offer.
C) Ask the employer if he or she knows of any other job openings.
D) None. If you don't respond, the employer will know you're not interested.