You Are About to Graduate as a RN

You are about to graduate as a RN. Your final term project is to prepare a presentation on HIV/AIDS. HIV (human immunodeficiency virus) is a retrovirus—it is an enveloped single-stranded virus that has duplicate copies of a single-stranded RNA genome. All retroviruses encode reverse transcriptase, an enzyme that uses an RNA genome as a template to make a complementary DNA strand. HIV can infect a variety of human cell types, but the most important are the helper T cells (also called CD4 cells) —the virus infects these cells and causes their death; their numbers slowly decline until the immune system can no longer resist infections or tumor development. You give your presentation to the class and are asked by your professor at the end of the session to answer some questions that your peers have on diagnosing HIV.
-One of your peers asks you to explain the term immunoassay. You tell him that it

A) is an in vivo test in which known antibodies or antigens are used to detect or quantify given antibodies or antigens.
B) is an in vitro test in which known antibodies or antigens are used to detect or quantify given antibodies or antigens.
C) is the study of in vitro antibody-antigen reactions, particularly those that detect antibodies in serum.
D) is an in vitro test that uses unlabeled antibodies to detect a very common antigen in a sample.
E) is an in vitro test in which unknown antigens are used to detect unknown antibodies.