What geological feature is at 0 years​

Paleozoic Era

Explanation:

The oldest is the Paleozoic Era, which means “ancient life.” Fossils from the Paleozoic Era include animals and plants that are entirely extinct (e.g., trilobites) or are rare (e.g., brachiopods) in the modern world.

i'm sure the answer you are looking for would be

a. an ice age

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