Radiometric dating is a method of dating geological or archaeological specimens by determining the relative proportions of particular radioactive isotopes present in a sample.

• A. It measures the relative proportions of isotopes in a sample
• B. It determines the relative proportions of particular radioactive isotopes present in a sample
• C. It uses fossil content to estimate age
• D. It relies on erosion rates to date samples

Answer: (B)

Radiometric dating relies on radioactive decay acting like a clock: certain isotopes are unstable and decay to daughter isotopes at a known rate. By measuring the proportions of a parent isotope and its daughter product in a sample, scientists can calculate how long the decay has been happening, converting the measured ratio into an age using the known half-life. This is why the statement focusing on the relative proportions of particular radioactive isotopes is the right description—it captures the specific, measurable relationship that provides the date. Measures that use general isotope content or rely on fossils or erosion don’t use this radioactive clock.