The diagram below represents a series of rock layers found at a particular location. each different type of shape shown in the layers represents a fossil of a different species.

suppose each symbol is related to a particular species in the following ways:
a red triangle represents a species of marine crustacean.
a green circle represents a species of jawless fish.
a yellow square represents a species of tree moss.
a purple star represents a species of forest-dwelling insect.
the change shown in the diagram at the end of the devonian geologic period could best be explained by
a.
the melting of a glacier and development of freshwater lakes and rivers.
b.
the environment changing from ocean to dry land.
c.
the arrival of a new predator in the ecosystem.
d.
the environment changing from a cold climate to a warm climate.