Why is radioactive decay a good method of measuring the absolute age of ancient fossils

All ancient fossils contain C-14

Explanation:

All living things contain more than one isotope of carbon, the most prominent being, carbon -12 and carbon-14.

Carbon-14 is a radioactive isotope of carbon. When the artifact is retrieved, the activity of carbon-14 in that sample is matched with the carbon-14 activity of a living organism. When this is done, the age of the fossil can easily be accurately calculated.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).