The Following Questions Refer to the Description Below

The following questions refer to the description below.
A lichen is a mutualistic association between a fungus and a green algae or cyanobacteria. There are clear morphological differences in lichen body form; some have flat bodies and are very close together, others have leaf-like bodies, and still others grow upright. The association between the two organisms is so complete that lichens are classified as a single organism.
-Biologists have noted that lichen structure differs substantially from the fungus component grown separately. What is the most plausible explanation for this?

A) The variation depends on the structure of the hyphae.
B) The variation depends if reproduction is sexual or asexual.
C) The variation is due to the photosynthetic partners which influence lichen structure.
D) The variation depends on the coevolution of the partners.
E) The variation depends where the lichens are found.