27.下圖為下列何者單糖之正確結構? (A) α-D-葡萄呋喃糖(a-D-glucofuranose) H HO CH₂OH (B) β-D-葡萄呋喃糖(β-D-glucofuranose) H H HO (C) a-D-葡萄吡喃糖(a-D-glucopyranose) OH H HO H (D) β-D-葡萄吡喃糖(β-D-glucopyranose)