A fossil is any natural evidence of prehistoric life that provides some idea of the size, shape, or form of the organism. A fossil does need not to be a whole animal or plant. Broken fragments are also fossils, as are the tracks left behind by the organisms. Fossils provide important evidence of how life and environmental conditions have changed. The fossils found in rock formations of different time periods differ because the environment on Earth has changed.
A paleontologist discovers a rock slab on which the footprints of a Pennsylvania dinosaur are well preserved. What does this fossil tell us about Pennsylvania?

A) rocks used to be really soft
B) you need bone to make fossils
C) animals are preserved as fossils
D) there was a time in Pennsylvania history when dinosaur existed