Concept:Carbon dating estimates the age of once-living materials by measuring the amount of radioactive carbon-14 remaining in them.Explanation:Carbon-14 is a radioactive isotope absorbed by living organisms. After death, the intake stops and carbon-14 decays at a steady rate. By comparing the remaining carbon-14 with a standard, scientists calculate the time since death. This method works for organic remains up to about 50,000 years old. It was developed by Williard Libby in the late 1940s and is a key tool in archaeology for dating bones, wood, cloth, and other ancient materials. It has revolutionised the dating of prehistoric events like the last Ice Age and the start of the Neolithic period. Therefore, carbon dating specifically refers to measuring the age of bones or materials found at ancient sites.Answer:D. Measurement of age of bones or materials in ancient sites