Final answer:
The correct answer is that the Earth is older than any rock layer, based on studies including geologic time scales and radiometric dating option number a is correct.
Step-by-step explanation:
Among the given options, the correct statement about the age of rock layers and the age of the Earth is: The Earth is older than any rock layer. Scientific evidence, including the study of geologic time scales, stratigraphy, and radiometric dating, has shown that the oldest known rocks on Earth are between 4 and 5 billion years old, which corresponds to the age of the Earth itself, estimated to be around 4.54 billion years old.
In a sequence of rock layers, the bottom layer is the oldest because the layers are deposited sequentially, with newer layers forming on top of older ones.