Identify the statement that is true about radiometric dating. choose one:

a. dating of metamorphic rock tells when the high temperatures of metamorphism cooled below the closure temperatures of the minerals involved.

b. it can be used only if some uranium is present in the rock.

c. dating of an individual sand grain in a sandstone accurately dates the sedimentary rock's formation.

d. it can begin only when the isotopes heat up enough to decay.