It is a good idea to accept a promotion interview, even if you're not interested in the promotion because

If your choices are the following:

a. Turning down a promotion you don’t want is easier after an interview

b. It could be good practice for the time you do want a promotion

c. Being able to use up your supervisor’s time will make you seem important

d. Having a promotion interview will give you an automatic wage increase

Then the answer would be B.