Seven persons P, Q, R, S, A, B, and D are sitting one above the other on a ladder (not necessarily in the same order). B sits neither at the top nor at the bottom. Only four persons sit between P and R. S sits immediately above A. Only one person sits between R and D. D sits below S. B sits above Q.

Three of the following are similar in a certain way based on their seating arrangement and form a group. Which of the following does not belong to that group?