`U^238` decays into `Th^234` by the emission of an a-particle. There follows a chain of further radioactive decays, either by `alpha`-decay or by `beta-`decay. Eventually a stable nuclide is reached and after that, no further radioactive decay is possible. which of the following stable nuclides is the end product of the `U^238` radioactive decay chain ?
A. `P b^(206)`
B. `P b^(207)`
C. `P b^(208)`
D. `P b^(209)`
