'R’ will be the first part of the given sequence as it begins with the word 'but' and is in contracts to S1. 'P' will logically come next as it further strengthens the point in 'R'. 'Q' will follow 'P' as it throws light on the issues mentioned before through an example. 'S' will come next as it begins with the words, 'In this room, which refers to the previous statement. Particular issue completes the belief stated in the previous statement. Hence, RPQS is the correct sequence. Thus, option (a) is correct.