Final answer:
The age of the upper layers of rock could only be younger than the base layer, which is more than 2 million years old; therefore, the answer is C, Between 2 million and 3 million years. Option C is the correct answer.
Step-by-step explanation:
If the age of the most layer of a rock sample is more than 2 million years, the age of the upper layers could be any of the following except greater than 3.5 million years. In geology, the principle of superposition states that in an undeformed sequence of sedimentary rocks, each layer of rock is younger than the one below it and older than the one above it. Therefore, if the oldest layer is more than 2 million years, the upper layers must be younger and thus, cannot be greater than 3.5 million years old.
Radiometric dating is a tool that allows us to determine the age of rock layers. The rocks at the Earth's surface were once molten and contain radioactive elements that decay at a predictable rate, providing a means to calculate their age. Some of the oldest known rocks on Earth have been dated to be around 4.4 billion years old through this method.
Considering the information above, the most reasonable answer to the question would be Between 2 million and 3 million years (option C) for the age of the upper layers of rock when the base layer is over 2 million years.