Answer: 3. root and mycelium
Plants are autotrophic organisms, which means they utilizes sunlight, atmospheric carbon and water, to prepare their own food in the form of carbohydrates. But these plants also requires some minerals like phosphorus, magnesium, nitrogen which are needed for their proper growth and metabolism. These plants obtain these minerals by absorbing them from the soil by the roots. Fungi are saprophytic organisms, which means they derive their food by decaying and decomposing the dead plants and animal traces. These fungi have thread like structures called as hyphae. The hyphae is responsible for penetrating the dead matter and obtaining nourishment. It functions like that of roots in plants. The aggregate of hyphae is called as a mycelium .
Therefore, both root and mycelium has a function in absorption of nourishment in the plants and fungi respectively.