A fossil is the remains of an animal or plant that lived long ago. Most fossils are created from the hard parts of an animal's body, ＿＿（41）＿＿ bones, shells, or teeth. Some are 42 , like dinosaur footprints. Some are so tiny that you need a microscope to 43 them. Most fossils are found in rocks 44 from the mud or sand that collects at the bottom of oceans, rivers, and lakes. Fossils provide scientists with 45 to ancient animals.