Concept:Half-life is the time taken for half of the radioactive atoms in a sample to decay, and it is a unique property of each radioactive element.Explanation:Every radioactive isotope has a characteristic half-life value.By measuring the half-life of a sample, scientists can identify which radioactive element or isotope is present.This makes half-life useful in detecting or identifying an element.It is not used to create, combine, or irradiate elements.Answer:B. Detect an element