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 D t-BuOK 1) MeMgBr; 2) H3O+ Na2Cr2O7,H2SO4,H2O NaOH H2. Lindlar's cat. 1) O3;2 ) DMS TsCl, py dilute H2SO4 1) LiAlH4; 2) H3O+ DMP or PCC 1) EtMgBr; 2) H3O+ 1) BH3.THF; 2) H2O2,NaOH