Fact 1: Most canyons are formed by flowing rivers through erosion over long periods of time. Fact 2: Deep canyons and valleys are carved out. Given the two facts above, what are formed by flowing rivers through erosion over long periods of time?
Options are:
[i] deserts.
[ii] a hydraulic system.
[iii] deep valleys.
[iv] pyramids.
[v] Calcium carbonate.
[vi] patch reefs.
[vii] buildings.
[viii] Sediment.
Answer:
[iii]