Flying Squirrels Eat Mushrooms That Decompose the Remains of Fir

Flying squirrels eat mushrooms that decompose the remains of fir trees - the dominant plants in the forest.Spotted owls eat the flying squirrels.In turn,crows eat the eggs of spotted owls.The fir trees are which of the following?

A) primary producers
B) primary consumers
C) secondary consumers
D) tertiary consumers
E) None of the above is correct.