The passage is primarily concerned with which of the following? A. tracing certain changes in the methods used to study the transmission of ancient Roman texts. B. contrasting two types of evidence used in investigating the transmission of ancient Roman texts. C. outlining certain difficulties associated with studying the transmission of ancient Roman texts. D. advocating the use of one type of evidence about ancient Roman texts over the use of another type. E. explaining the development and potential uses and drawbacks of stemma in the study of ancient Roman texts.