In a Prosecution in a Criminal Case, Testimony Taken at a Previous

In a prosecution in a criminal case, testimony taken at a previous trial may sometimes be admitted. The rule concerning admissibility is that:

A) such evidence is admissible for the prosecution unless the defense counsel can prove that the witness is available to testify at the trial.
B) the fact that a witness is pregnant at the time of trial is sufficient to show unavailability.
C) where testimonial evidence is involved, there must be a trial opportunity to cross-examine the witness or a proper earlier proceeding where the right of cross-examination existed and there must be proof of unavailability of the witness.
D) the witness's testimony given at a prior state court hearing cannot be considered by a federal court in the future.