Igneous rock has turned into sedimentary rock. Igneous rock has turned into metamorphic rock. Sedimentary rock has turned into igneous rock. Sedimentary rock has turned into metamorphic rock.
I gave my students this multiple choice question: A rock formation in a land area contains fossils. Over time, tremendous heat and pressure change the formation to produce a harder rock formation without fossils. Which change in rock type has occurred in this land area?

Only one answer is correct among these 4 choices:
- Igneous rock has turned into sedimentary rock.
- Igneous rock has turned into metamorphic rock.
- Sedimentary rock has turned into igneous rock.
- Sedimentary rock has turned into metamorphic rock.

Could you tell me which one is correct?

Sedimentary rock has turned into metamorphic rock.