【名词&注释】
复杂度(complexity)、可行性、正确性(correctness)、健壮性(robustness)、图的邻接矩阵(adjacency matrix of graphs)
[单选题]N个顶点,e条边的无权有向图的邻接矩阵(adjacency matrix of graphs)中非零元素有()个。
A. n B. n-e C. e D. e+