问题：
[单选题]
For problem X, now we get a 3-approximation algorithm. Which of the following statement is TRUE?
AThere is no ρ-approximation algorithm for X for any ρ<3.
BProblem X is NP-hard.
CThe algorithm can give a solution for any instance of problem X within ratio 3 of true optimum.
DProblem X can be solved in polynomial time.
