(5). Given the adjacency matrix of a directed graph as the following: 0100100001011100 The out-degree and the in-degree of the vertex 2 (the index starts from 0 ) are ( ), respectively. (A) 3 and 1 (B) 1 and 3 (C) 0 and 2 (D) 2 and 0 (6). If an undirected graph has 3 vertices, then it must have at most edges. (A) 2 (B) 3 (C) 6 (D) 9 (7). A tree is the most suitable structure to represent ( ). (A) sorted elements (B) unsorted elements (C) elements with no direct relation (D) elements with hierarchical branching relations (8). Among the following statements about adjacency matrix, which one is TRUE? ( ). (A) The adjacency matrix of a directed graph is never symmetric (B) The adjacency matrix of a directed graph may or may not be symmetric (C) The adjacency matrix of an undirected graph is never symmetric (D) The adjacency matrix of an undirected graph may or may not be symmetric (9). Prim's algorithm is a ( ). (A) Divide and conquer algorithm (B) Greedy algorithm (C) Dynamic Programming (D) Approximation algorithm (10). Among the following methods, which one is stable? (A) Heap sort (B) Shell sort (C) Merge sort (D) Quick sort