What Does It Mean for the International Criminal Court (ICC)to

What does it mean for the International Criminal Court (ICC) to be a court of last resort?

A) Plaintiffs must use all of their national appeals before taking a case to the ICC.
B) The United Nations must take a case to the Security Council for mediation before it can come before the ICC.
C) Only those who live in countries that have not ratified the ICC can bring cases.
D) The court will only hear a case if there is no other feasible method of resolving it.
E) It cannot act if a national judicial authority has already prosecuted the case.