What parts of a living thing are most likely to be preserved as a fossil?why?

Question

What parts of a living thing are most likely to be preserved as a fossil?why?

Answer 1

Bones and other calcium type material (teeth, etc) because they are the most dense material found in living organisms and decompose at a far lesser rate then any other material or cells.

Answer 2

Most obviously the bones because flesh rots quickly and is eaten by bugs and animals.  Following on this is scales, hair, and feathers which are tougher materials than flesh, which may survive in recognizable form if buried quickly in fine mud where it is protected from damage.