'P’ will be the first part of the given sequence as it begins with the word 'that' which indicates that this sentence talks about the belief. 'R' will logically come next as it completes the belief stated in the previous statememt statement. 'Q' will come next as it tells about how this belief 'still exists' and 'S' will logically complete the sequence with 'Q'. Hence PRQS becomes the right sequence of words. Hence, option (a) is correct.