‘R’ will be the first part of the given sequence as it begins withthe words, ‘In the course of time’ and takes the information provided in S1 forward. ‘P’ will come next as it refers to the word, ‘atmosphere’ which is mentioned in the previous statement. ‘S’ will come next as it is in continuation with the previous statement which is clearly indicated form the word, ‘This early atmosphere’. ‘Q’ will follow logically as it tells the reason for the cause of the previous statement. Hence, RPSQ is the correct sequence.Thus, option (a) is correct.