Ans. (b). fungi.
Mushrooms or toadstool are spore-bearing, fleshy fungal organisms, having a domed cap on their stalk and gills on the lower side of cap. They be be edible (non-poisonous) or poisonous on the basis of their composition.
Fungi are often mistaken as plants as they also have rigid cell wall and they row out of the soil like plants. Mushrooms are placed in kingdom fungi, which includes eukaryotic, multicellular, heterotrophic organisms that feed through their mycelia.
Thus, the correct answer is option (b).