The correct sequence is RPSQ. The sentence SI describes that Mr. Sherlock Holmes and Dr. Watson are spending a weekend in University town. The next sentence should be R because it is in continuation of SI and describes where they are staying. The next sentence should be P because it describes the event that they get visited by Mr. Soames. Next sentence should be S because it describes Mr. Soames. The next sentence should be Q because it describes his state of mind and is in continuation of the S6 sentence.