The hyphae of arbuscular mycorrhizal fungi (AMF) form bushy structures after making contact with the plasma membrane of a root cell. What is the function of these structures?a. They anchor the fungus inside the root, so the association is more permanent.b. They increase the surface area available for the transfer of nutrients.c. They produce toxins that protect the plant cells against herbivores.d. They break down cellulose and lignin in the plant cell wall.