Answer: B.The layers within the rock
Step-by-step explanation:
Sedimentary rocks are simply referred to as the rocks that are formed from the rocks that were already in existence before.
The are gotten from the deposits of living organisms or rocks that are on the surface of the Earth which consolidate. Due to this consolidation of the sediments which take a period of years, they form layers.
Therefore, Declan concluded that the rock was sedimentary because of the layers that were within the rocks.