A rock with different fossils is shown below:

A diagram labeled Fossil Layers is shown. The topmost layer is labeled Fish and shows the skeleton of a fish, the second layer from the top is labeled Shell and shows a shell, the third layer from the top is labeled Fern and shows a fern leaf, and the lowermost layer is labeled oak and shows an oak leaf

Based on the fossil, which statement is correct?

The fern evolved after the fish.
The oak evolved after the fern.
The fern evolved after the shell.
The shell evolved after the fern.