Radiometric dating can be used to determine the amount of time since a. a rock most recently solidified. b. a rock first solidified. c. the elements in a rock were formed inside stars or a supernova. d. the big bang.

The correct answer is B: "Radiometric dating can be used to determine the amount of time since a rock first solidified".

Explanation:

In geology, the radiometric method is used to determine the age of a rock. It is based on the natural radioactive decay of certain elements, isotopes. Each radioactive element decays at a constant known rate, which is unique to that element. Measuring the proportion of original isotopes and the newly formed isotopes can tell when the rock was first formed. Before determining the age of the rock, it must be analyzed to make sure that the original minerals have not been altered since the rock first formed. Radiometric age determinations are very expensive, so geologists must be sure that the age of the rock will help to answer an important research question.  

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