What process involves observing the natural decay of radioactive elements?

The correct answer is related to the method used to determine the age of materials by observing the decay of radioactive isotopes. This technique is known as radiometric dating, which applies the principles of radioactive decay to calculate the age of rocks, fossils, and other geological or archaeological samples.

Radiometric dating relies on the steady and measurable rates at which radioactive isotopes decay into stable daughter products over time. By measuring the remaining amount of the radioactive element and knowing its half-life—the time it takes for half of the original isotope to decay—scientists can estimate how long it has been since the rock or organic material was formed.

Carbon dating is a specific type of radiometric dating used for dating recent organic materials (like wood or bone) using the radioactive isotope carbon-14, while fission and fusion refer to nuclear reactions that involve splitting or combining atomic nuclei, respectively. These processes do not specifically relate to the observation of the decay of elements for dating purposes.