I"m not really sure but i think the answer is C.
An artistic movement that chose to focus on unidealized subjects that were previously not shown through art work.
The principle of superposition states that the oldest sedimentary rock units are at the bottom, and the youngest are at the top. Based on this, layer C is oldest, followed by B and A. So the full sequence of events is as follows: Layer C formed.
I believe the answer you are looking for is Tributary.