With no explanation, chose the best option from "A", "B", "C" or "D". to prevent the declarant from testifying” as also being constitutionally required to admit the hearsay of an f undercover police officer involved with the defendant in drug transactions while in the process of arresting the defendant); United States v. Thevis, 665 F.2d 616, 630 (5th Cir.1982) (“We conclude that a defendant who causes a witness to be unavailable for trial [by murdering him] for the purpose of preventing that witness from testifying also waives his right of confrontation[.]”); Steele v. Taylor, 684 F.2d 1193, 1199, 1201 (6th Cir.1982) (concluding that the constitutional waiver was applicable where the defendant caused a witness under his control to refuse to testify based on the fifth amendment privilege); United States v. Balano, 618 F.2d 624, 629-30 (10th Cir.1979) (<HOLDING>), overruled on other grounds as recognized by

A: holding that where witness refused to take the oath and testify his grand jury testimony should not have been admitted because he was not subject to cross examination before the grand jury
B: holding that testimonial hearsay statements of a witness who does not appear at trial are inadmissible under the confrontation clause of the sixth amendment unless the witness is unavailable to testify and the defendant has had a prior opportunity to crossexamine the witness
C: holding that witness grand jury testimony was admissible when defendant waived his constitutional right of confrontation by making witness unavailable by threats to his life
D: holding that promises made by the prosecution to a witness in exchange for that witness testimony relate directly to the credibility of the witness
C.