‘S’ will be the first part of the given sequence as it is in contrast to with the given sentence as it tells us about what happened next which is clearly indicated from the words, ‘The clerk asked for the sales receipt but after searching his pockets the man replied that he had lost it’. ‘P’ will come next as it further takes the conversation forward and represents the consequences of the information given in the previous sentence, that is, ‘He said that free alteration is not possible without a receipt’. ‘Q’ will come next as it is in continuation with the previous statements which is indicated from the words, ‘The man said, 'Okay. I'd like to return the trousers.' The clerk took them back and returned the money’. ‘R’ will follow logically as it is in contrast to the previous statement which is indicated from the words, ‘The man pushed the money and said’. Hence, SPQR is the correct sequence. Thus, option (b) is correct.