Answer:
b. All rocks in the Earth's crust will, at some point, be subducted and melted to create igneous rock.
Explanation:
There are 3 types of rock:
1. Igneous, wich are formed when 2 tectonic plates collide and magma goes to surface getting cold
2. Sedimentary: when many layers of preexistent rocks produce pressure and heat by weigth melting the rocks.
3. Metamorphic: a new rock is formed by chemical and/or physical reaction over preexistent rocks
Sedimentary and metamorphic would be subducted in order to produce new igneus rocks.