With no explanation, chose the best option from "A", "B", "C" or "D". the agreement's direction to seek legal advice, a separate statutory requirement for a valid waiver, see § 626(f)(1)(E), for clarification of the waiver would ‘ nullify the distinct requirement, that the agreement be written in a manner calculated to be understood by the participant (as opposed to his attorney). 2 . IBM agreed at oral argument that if we found the waiver deficient under the statute, we need not decide the proper test to apply to determine whether the waiver was also knowing and voluntary. Compare Ulvin v. Northwestern Nat'l Life Ins. Co., 943 F.2d 862, 866 & n. 4 (8th Cir.1991) (applying contract principles to pre-OWBPA waiver), cert. denied, 502 U.S. 1073, 112 S.Ct. 970, 117 L.Ed.2d 135 (1992), with Bennett v. Coors Brewing Co., 189 F.3d 1221, 1228-29 (10th Cir.1999) (<HOLDING>). We leave that discussion for another

A: holding a waiver of a substantial constitutional right must be a voluntary knowing and intelligent act
B: recognizing that courts will enforce waiver of appeal rights when waiver is knowing and voluntary
C: holding that a defendant must demonstrate a knowing waiver
D: holding that even if statutory requirements are met courts must inquire into totality of the circumstances to determine if waiver was knowing and voluntary
D.