18 The is a greedy algorithm ut of Select one: a BFS search stion b. Prim's algorithm O c. mergesort d. DFS search When does a hash table need to be rehashed? Select one: a. As soon as the table is half full O b. When an insertion fails c. When the table reaches a certain load factor d. a or borc In the FirstChild-NextSibling representation of a nonempty tree, NextSibling pointer of root node Select one: O a. must not be NULL O b. may be NULL c. must be NULL