Propose an efficient synthesis for the following transformation: The transformation above can be performed with some reagent or combination of the reagents listed below. Give the necessary reagents in the correct order, as a string of letters (without spaces or punctuation, such as "EBF"). If there is more than one correct solution, provide just one answer. A. HBr B. NaOEt C. EtBr D. NBS, heat E. conc. H2SO4, heat F. H2SO4,H2O,HgSO4