When animals, plants and other organisms die, they typically decay completely. But sometimes, when the conditions are just right, they're preserved as fossils.
Several different physical and chemical processes create fossils, according to the New York State Geological Survey. Freezing, drying and encasement, such as in tar or resin, can create whole-body fossils that preserve bodily tissues. These fossils represent the organisms as they were when living, but they're very rare. Most organisms become fossils when they're changed through various other means. The heat and pressure from being buried in sediment can sometimes cause the tissues of organisms — including plant leaves and the soft body parts of fish, reptiles and marine invertebrates — to release hydrogen and oxygen, leaving behind a residue of carbon.
What title could be best assigned to the above passage?
A. How fossils are formed.
B. How fossils are preserved.
C. How animals decay.
D. How fossils are changed.