Answer:
Autotrophs are the organisms which have photosynthetic pigment chlorophyll which traps the energy of the sunlight and synthesis their own food.
Fungi are a group of eukaryotic organisms which belong to Kingdom Fungi they synthesize their own food like plants but are dependent on plants and animals dead decaying matter to derive nutrition for food synthesis. As, they also not possess chlorophyll pigment necessary for trapping the sunlight energy which the quality of plants which are consider as autotrophs. They cannot be consider as autotrophs.
Also the cell wall of fungi is made up of chitin which is also present in some animals whereas the cell walls of plants is made up of cellulose. Although both plants and fungi grows over the soil but fungi has an decomposition action on the dead organisms underlying the soil causing synthesis of simpler organic matter which can be easily taken up by fungi as well as plants.