Correct Option: D

Uranium–lead (U–Pb) dating is one of the oldest and most refined of the radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1–1 percent range. The method relies on two separate decay chains, the uranium series from 238U to 206Pb, with a half-life of 4.47 billion years and the actinium series from 235U to 207Pb, with a half-life of 704 million years. These decay routes occur via a series of alpha (and beta) decays, in which 238U with daughter nuclides undergo eight total alpha and six beta decays whereas 235U with daughters only experience seven alpha and four beta decays. The existence of two ‘parallel’ uranium-lead decay routes (238U to 206Pb and 235U to 207Pb) leads to multiple dating techniques within the overall U–Pb system. The term U–Pb dating normally implies the coupled use of both decay schemes in the ‘concordia diagram’.