Question 2
Based on the above data, answer the given subquestions.
The TRIANGLE-FREEDOM problem is the following: the input is a simple undirected graph G and a positive integer k. An instance (G, k) is a YES-instance if and only if G has a subset S of at least k vertices that are triangle-free.
What can you say about TRIANGLE-FREEDOM? Check all that apply.
It is in P.
It is in NP.
It is NP-hard.
It is NP-complete.