The difference between a stone-tool mark and a tooth mark is that:
a. tooth marks leave smooth grooves, and stone-tool marks leave many parallel grooves.
b. tooth marks occur along the entire shaft of the bone, but stone-tool marks occur only at the end of the bone.
c. stone-tool marks are crooked because hominins were not skilled at using stone tools.
d. stone-tool marks contain stone flake residue.