Answer
Information now travels from RNA to DNA only in the replication of retroviruses, involving the enzyme reverse transcriptase which is far from common if one considers the whole biological world. Normally information flows from DNA to RNA. What would be required early in the history of life is an enzymatic activity similar to reverse transcriptase.
Work Step by Step
This question is asking you to review the process of gene expression (Ch. 17) and the actions of retroviruses (Ch. 19) as hints towards understanding both the normal flow of genetic information today and how this could have been reversed early during the history of life.
