With no explanation, chose the best option from "A", "B", "C" or "D". affirm. The district court properly dismissed the action because the United States — the only proper party — met the requirements of the discretionary function exception. See 28 U.S.C. § 2679(d)(1) (providing that, upon certification that employees were acting within scope of their U.S. government employment, the action shall be deemed an action against the United States which shall be substituted as the defendant); Terbush, 516 F.3d at 1129 (recognizing discretionary function exception applies if (a) the government’s conduct was discretionary, with no federal statute, regulation, or policy prescribing a specific course of action, and (b) the action or decision involves considerations of public policy); In re Consol. U.S. Atmospheric Testing Litig., 820 F.2d 982, 993-999 (9th Cir.1987) (<HOLDING>). The plaintiffs’ remaining contentions,

A: holding discretionary function exception applied to claims against united states for radiation exposure from nuclear weapons testing
B: holding that prosecution of defendant in the united states for hostage taking based on acts committed outside the united states did not violate due process
C: recognizing federal constitutional claim against the united states
D: recognizing similar problem if fca is applied to claims presented to any federal grantee even if claims are not represented to united states
A.