Which of the following statements best describes the function of the highlighted sentence in the context of the passage as a whole? A. It notes a fact about Timurid rugs, that explains why they have been the subject of scholarly controversy. B. It emphasizes the fragility of central Asian textiles from the period in question. C. It situates Timurid rugs within the wider context of textile arts from the same period. D. It suggests why the author is relying upon indirect evidence for the dating of trends in Timurid rugs. E. It describes a constraint on the study of Timurid rugs that the author thinks has been overemphasized.