What are three different types of canyons? How are they formed?

Over thousands of years a river's flowing water erodes or wears down rocks and soil to create a valley. The largest and most popular canyons have had slit through dry areas by swift streams sustained by rain or melting snow from wetter areas.

answer is  

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to prove that the triangles are congruent using the aas congruence

answer they showed that organic molecules such as amino acids could be produced from inoragnic molecules;