Question 9 10 pts Select all the answers below which are TRUE A greedy algorithm is a top-down approach. O To use the greedy algorithm discussed in class for solving the activity selection problem, all the activities have to be sorted in monotonically increasing order of their starting time. Let Z be an LCS of two sequences X and Y. Then the length of Z is at least half of the length of X The running time for solving the Longest Common Subsequence using Brute Force is O(n). The running time of the GREEDY-ACTIVITY-SELECTOR (sf) algorithm is O(ngn) if the input activities are not sorted. LCS-Length(X,Y) algorithm has the running time RT O(mn), where n is the length of X and m is the length of Y. A greedy algorithm does not always yield to an optimal solution, but for some problems it does compute an optimal O O solution