Your answer is D, Rhizobium
Fungi cell walls are made of chitin and other polysaccharides, not cellulose (Plants) or protein (Animals). Therefore your answer is-
"The cell walls of fungi are different than the cell walls of plants because they contain the hard material of chitin"
"PRODUCERS" are always found at the base of a food chain.
The answer to this question is CCR or Central Contractor Registration. The CCR was the main supplier database intended for the United States Federal government. The CCR is the source where it collected data from suppliers, validated and stored the data, disseminated it to various branches in the government acquisition agencies.
The foreign molecule that activates the immune system are Antigens.