All of the following are true of a radionuclide effective half-life EXCEPT:

a. It takes into account the relationship between physical and biologic half-lives.
b. It is the product of the physical and biologic half-lives divided by the sum of the physical and biologic half-lives.
c. It is always shorter than either the physical half-life or biologic half-life.
d. It is of little importance as a consideration of radionuclides used for medical diagnosis.

d. It is of little importance as a consideration of radionuclides used for medical diagnosis.