What Is the Primary Reason That Fungi Are Important in the Carbon

What is the primary reason that fungi are important in the carbon cycle?

A) Fungi are able to reach incredibly large sizes, storing carbon while they are alive, and contributing carbon back to the atmosphere when they die and decompose.
B) Fungi are able to reach incredibly large sizes. Their high ratio of surface area to volume allows them to decompose large amounts of dead/decaying material, thereby returning carbon to the atmosphere.
C) Fungi are able to reach incredibly large sizes. They have a high ratio of surface area to volume and are able to fix more carbon through photosynthesis than other plants of comparable size.
D) Fungi are able to reach incredibly large sizes. Their high ratio of surface area to volume allows them to store more carbon (in the form of sugar) obtained through mycorrhizal associations than their symbiotic hosts.