The correct answer is option 2: Fungi. Mushrooms are a type of fungi. Fungi are a distinct group of organisms that are neither plants nor animals. They are characterized by their ability to absorb nutrients from their surroundings. Mushrooms are the reproductive structures of certain types of fungi.

Option 1: Algae. Algae are a diverse group of photosynthetic organisms that are primarily aquatic. They are not related to fungi or mushrooms.

Option 3: Lichens. Lichens are actually a symbiotic relationship between a fungus and an alga or a cyanobacterium. While fungi are involved in lichens, mushrooms are not directly related to lichens.

Option 4: Parasitic moss plants. This option is incorrect as mushrooms are not parasites of moss plants. Moss plants are separate organisms from mushrooms and fungi.

In conclusion, mushrooms are a type of fungi, and they are not algae, lichens, or parasitic moss plants.