Answer:
D. Layers with similar fossils
Step-by-step explanation:
Dating consists of ordering geological events according to the time they occurred, which ones occurred first, and which ones occurred latterly. This dating can be done by using the superposition geological principle. This principle states that in a horizontal unperturbed rocky sequence, the oldest layers or stratum are located in the bottom, while the newest ones are more superficially located. Sediments can be incrusted in horizontal layers or stratum. Fossils that are incrusted on these layers represent different ages of the stratum. Different stratum can give us information about the environment in the past. They keep information about the age and the conditions under which the sediments got deposited.
Some geological principles allow us to date, relatively, the age of different geological events in the past.
Sediment layers place in a temporal sequence, let us know that the older layers are located in an inferior position concerning the newer layers. Hence, fossil species placed in more inferior layers are supposed to be older than fossil species found in more superficial layers.
In this sense, those layers or stratum that exhibit the same fossils are believed to be the same age-old.