11. Choose the best conditions to achieve the following stereospecific transformation:

(A) 1. Mg 2. CO₂ 3. H⁺
(B) 1. KO^tBu ₂. HBR3 3. H₂O₂, NaOH
(C) 1. NaOAc 2. H₂O, H⁺
(D) 1. KOH 2. PCC, H₂O

(E) 1. NaCN 2. KOH, H₂O 3. H+, H₂O

（SN2 機制）與立體化學特性（構型翻...