A:π6
B:π4
C:π3
D:π2
—Mum, I am hungry.
—Here is a for you. Why not help yourself to it?
地衣中的藻类通过光合作用为真菌提供有机物,真菌为藻类提供水和无机盐.地衣中的藻类与真菌的关系是( )