the water of oceans. the ice on ponds. the trunks of trees. rocks in the ground.
I gave my students this multiple choice question: The fossils of dinosaurs that lived millions of years ago can be found in

Only one answer is correct among these 4 choices:
- the water of oceans.
- the ice on ponds.
- the trunks of trees.
- rocks in the ground.

Could you tell me which one is correct?

rocks in the ground.