7. Which of the following explains how radiometric dating is used to estimate absolute
age.
a. By comparing how deep in the curst the radioactive material in a sample of rock
is, scientists can calculate the length of time since the rock formed.
b. By comparing the amount of organic material in a sample of rock, to the known
rate of decay of the parent rock, scientists can calculate the length of time since
the rock formed.
C. By comparing the amount of radioactive material in a sample of rock, to the
surrounding rocks, scientists can calculate the length of time since the rock
formed.
d. By comparing the amount of a radioactive material in a sample of rock, to the
know rate of decay of the parent rock, scientists can calculate the length of time
since the rock formed.

Radiometric dating is a method of dating geological/ archaeological specimens by determining the relative proportions of particular radioactive isotopes present in a sample. Carbon dating is a form of radiometric dating, but, in choice b, you're not comparing the carbon to the rock. One would compare ¹⁴C levels within the organic compound, just as one would compare radioactive isotope levels in a rock.