What is the most appropriate action to take after your interview?

starting to assemble an appropriate wardrobe for your new job
phoning the next day to the interviewer and ask if you've been hired
announcing your new position to friends on your social networking site
writing a brief note the interviewer and expressing your interest in the position

D). Writing a brief note thanking the interviewer and expressing your interest in the position.

Explanation:

As per the question, the most appropriate action to be taken or reaction to be displayed post an interview is to acknowledge and express your gratitude towards the interviewer that would reflect your etiquette and present a positive image of yours before him. Thus, 'writing a brief note to thank the interviewer which would mirror your interest in the position'. Therefore, option D reflects the right reaction to be displayed after an interview.