(a) autoradiography

Explanation:

Autoradiography is the use of X-ray films to detect radioactive material. It produces a permanant record of positions and relative intensities of radiolabeled bands in a gel or slot. Typically, biomolecules are labeled with 32P or 35 S, and detected by over night film exposure.

Autoradiography technique may be used to determine the tissue localization of a radioactive substance, either introduced into a metabolic pathway, bound to a receptor or enzyme, or hybridized to a nucleic acid.