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 reagent(s) 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 B C tBuOK 1) O3;2)DMS Br2,hv D E F H2SO4,H2O,HgSO4 H2, Lindlar's cat. HCCNa G H I HBr HBr,ROOR 1) R2BH;2)H2O2,NaOH