Substances such as enzymes, antigens, and hormones present in the circulation that can be used for cancer screening, to confirm a diagnosis, or to monitor the clinical course of a malignancy are called:

Analytes.

Explanation:

An analyte is a substance/bio-molecule which is being analyzed with the help of a laboratory procedure or test.  

In case of cancer, the cancerous cells produce different analytes (enzymes or antigens or hormones) than the normal cells do. So if we detect a different analyte than the normal analyte then we can easily infer that the person being analyzed has cancer.  

i would say the prokaryotic cells the prokaryotic cells are less complex, are usually found only in unicellular organisms and have more limited capabilities than eukaryotic cells.

i'd say that the moon rock is about 2.2 billion years old.