Hint: The word fungi refers to the eukaryotic organisms which include microorganisms like yeast and mold. Fungi do not produce their own food. Therefore, they are called heterotrophs. The fungi which have a symbiotic relationship with the plant are known as mycorrhiza.
Complete answer: The unicellular microorganisms such as yeast, mold, and mushroom are fungus. Fungus belongs to the group of eukaryotic organisms. They do not regulate the function of photosynthesis and hence cannot produce their own food. Therefore, they are called heterotrophs. The characteristic feature of microorganisms belonging to kingdom fungi contain chitin in their cell wall. This makes them different from the plants and animals. Hence, they are grouped as a different kingdom called fungus. The term mycorrhiza stands for the mutual association of the fungus with the plant. There are two types: ectomycorrhizal fungi and endomycorrhizal fungi. Ectomycorrhizal fungi are responsible for exchange mechanisms outside of the root cells and endomycorrhizal fungi are responsible for the mechanism inside of the cell. In endomycorrhizal fungi the part of fungi such as hyphae or thread-like structure actually penetrates into the soil for the benefit of the plant. Some of the examples of endomycorrhizal fungi are Glomus, ericoid mycorrhizas and etc. therefore, option B is the correct answer.
So, option B is the correct option.
Note: Fungus play an important role in the decomposition of the organic matter. It also plays a vital role in nutrient cycle and exchange in the environment. Endomycorrhizal fungi form symbiotic relationships with almost 80% of plant families. Some of the examples of ectomycorrhiza fungi are Basidiomycota, Amanita, Boletus.