Carbonized fossils are made of: O the carbon remains of the original organism
O carbon which replaced the plant or animal
O a cast of coal
O a mold left in coal

Carbonized remains are thin, approximately two-dimensional films of carbon preserved on a flat surface of rock. They are most often black in color, reflecting the fact that they composed mostly of carbon (as is coal, which is also black in color). Most fossils that exhibit “soft part” preservation are carbonizations.

I would say the answer is the Carbon remains of the original organism.