‘S’ will be the first part of the given sequence as it is in continuation with the previous statement and refers back to the information talked about in S1. ‘P’ will follow next as it begins with the word, ‘whenever, and presents a situation related to ‘S’. ‘R’ will come next as it is in continuation with the previous statement which is clearly indicated from the word, ‘Thus’. ‘Q’ will follow logically as it sets the conclusion of the passage. Hence, SPRQ is the correct sequence. Thus, option (c) is correct.