the age of the rock the slope of the rock the density of the rock the weathering of the rock
Scientists found trilobite and brachiopod index fossils in cliffs a great distance apart from each other. What can scientists infer about the rocks in which these fossils were found?

Options:
- the age of the rock
- the slope of the rock
- the density of the rock
- the weathering of the rock

the age of the rock