An example of a mutualistic association between a plant and a fungus would be

mycorrhiza

Explanation: mycorrhiza is the symbiotic relationship that occurs between a fungi and the root of plants.here the fungi helps the plant absorbs nutrients and water from the soil.the fungi encloses the root and it's hyphae penetrates into the root cell.the fungi in return gets food from the plant.in this interaction,they both benefit.

The association may be ectomycorrhizal or endomycorrhizal. In ectomycorrhizal,the fungi grows on the surface of the root and it's hyphae coats the roots.in endomycorrhizal,the fungus does not necessarily coat the root,but few hyphae penetrates the epidermal cell and the cortex of the root.it is said to be living within the cells of the root.

d. organisms have cells with different shapes and functions.