‘S’ will be the first part of the given sequence as it begins withthe word, ‘that’. ‘P’ will follow next as it clarifies what was the effect of the first action, that is, ‘he sat down under a tree’. ‘R’ and ‘Q’ will follow logically as ‘R’ begins with the conjunction ‘and’ and connects ‘P’, ‘R’ and ‘Q’. Hence, SPRQ is the correct sequence. Thus, option (b) is correct.