金黄色葡萄球菌细胞壁肽聚糖单体四肽尾的氨基酸残基排列顺序为（）

A.L-Ala—D-Glu—L-Lys—D-Ala

B.D-Glu—L-Ala—L-Lys—D-Ala

C.L-Ala—L-Lys—D-Glu—D-Ala

D.D-Ala—D-Glu—L-Lys—L-Ala

正确答案：L-Ala—D-Glu—L-Lys—D-Ala