单项选择题
A.12 B.24 C.48 D.72
A.⑤—③—②—①—④ B.②—⑤—③—①—④ C.②—③—⑤—④—① D.⑤—②—③—④—①
A.④—②—①—③ B.④—①—②—③ C.③—④—②—① D.③—②—④—①