单项选择题
A.2B.3C.4
A.Σ(ABCD)(1,2,3,6,8,11,14)B.Σ(ABCD)(1,2,3,7,8,13,14)C.Σ(ABCD)(1,2,4,6,8,11,14)D.Σ(ABCD)(1,2,3,6,8,13,14)
A.6个B.7个C.8个D.9个