'R' will be the first part of the given sequence as it is in contrast with the given sentence which is clearly indicated from the words, ‘No one could have expected’. ‘Q’ will come next as it is in continuation with the previous statement, that is clear from the word, ‘All his usual'. 'S' will come next as it brings a new idea into the passage. 'P' will come at the end as it refers back to the previous statement. Hence, RQSP is the correct sequence. Thus, option (a) is correct