The passage opens with the dinosaurs’ scientific description. S adds to its further description by stating that it was 40 feet in length. R elaborates the details of the dinosaurs further. R mentions the ‘teeth’ of the dinosaurs and P adds to the description of it so it is the next to come. Q tells us about its limbs. S6 concludes the passage by stating its history. SRPQ is the correct sequence. Hence, (b) is the correct option.