The three groups of rocks are classified by a. color b. how they formed c. chemical composition d. grain size

Option B

Explanation:

The three groups of rocks such as sedimentary, metamorphic and igneous rocks are classified based on how they are formed inside the earth.

These forms of rocks keeps on interchanging among them. Under immense pressure the molten materials cool down to form rock crystals.

These crystals when stay for a longer duration of time the crystal size increases to form larger crystals of rock.

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