单项选择题
A.n(n+1)/6 B.n(n-1)/6 C.n2/6 D.(n+1)(n-1)/6
A.520 B.89 C.179 D.180
A.(102,87,100,79,82,62,84,42,22,12,68) B.(102,100,87,84,82,79,68,62,42,22,12) C.(12,22,42,62,68,79,82,84,87,100,102) D.(102,87,42,79,82,62,68,100,84,12,22)