Most Coal Was Formed During the Carboniferous Period

Multiple Choice

Most coal was formed during the Carboniferous period.What is a reasonable hypothesis that explains this observation?

A) Plants from this period did not require fungal associations.
B) There were not many saprophytic fungi during this period.
C) There were not many mycorrhizal fungi during this period.
D) Coal was formed from an explosion of fungal species during this period.