The true statement is:
Imprints of leaves or footprints in sedimentary rock are fossils.
Fossils can include various forms of preserved remains, such as imprints, and the other options provided are incorrect. Petrified remains, such as skeletal bones, are indeed considered fossils, insects in tree sap (amber) are also classified as fossils, and recent remains on topsoil are not classified as fossils since they haven't undergone the fossilization process.