The amount of a certain isotope that occurs in a natural sample of an element? is what

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What is "the ring of fire"? a. a type of volcanic eruption b. an area around the pacific ocean c. a circle of volcanoes forming over a hot spot d. a region around a cinder cone in which ash is likely to land

Plz ! if the age of the lowermost layer of a rock sample is more than 2 million years, which of the following could be the age of the upper layers?