the age of the rock the slope of the rock the density of the rock the weathering of the rock
I gave my students this multiple choice question: 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?

Only one answer is correct among these 4 choices:
- the age of the rock
- the slope of the rock
- the density of the rock
- the weathering of the rock

Could you tell me which one is correct?

the age of the rock