When May a Witness Invoke the Privilege Against Self-Incrimination

When may a witness invoke the privilege against self-incrimination?

A) When the witness knows that the answer will subject him or her to the danger of prosecution and conviction.
B) When the judge is satisfied that the answer would be incriminating.
C) Only when the witness is testifying in a criminal trial.
D) Only when the answer would be a complete admission of guilt.