Answer: Answer is B, Younger than 400 million years
Step-by-step explanation:
The age of rock layers in a stack reflects the order in which they were deposited—the lower layers were laid down first, and then the upper layers were laid on top of them. So, the lower layers and fossils they contain are older than the upper layers and fossils. This is known as the principle of superposition.
In this example, Layer 1 was deposited first, then Layer 2, Layer 3, Layer 4, and Layer 5. Layer 1 is the oldest, and the layers get younger as you move up through the stack.
If the age of a particular layer is known, then the relative age of other layers can be determined. In this example, Layer 4 is 400 million years old. This means that the layer above it is younger than 400 million years and the layers below it are older than 400 million years. Layer 1 is 500 million years old. This means that layers above it are younger than 500 million years.
Layer 5 is above Layer 4, so it must be younger than 400 million years.