One Issue That Arises When Relative Dating Using the F-U-N

One issue that arises when relative dating using the F-U-N trio is that

A) mineral content of bones reflects mineral content of the groundwater in the area.
B) bones and teeth undergo transformation in chemical composition when buried for long periods.
C) older fossils contain greater amounts of fluorine.
D) older fossils contain smaller amounts of nitrogen.
E) this method does not examine carbon content of fossils.