Concept:Corms, rhizomes, and tubers are underground plant structures that act as modified stems for food storage and vegetative propagation.
Explanation:Although they grow below the soil, these structures are not roots.
They possess nodes, internodes, and buds, which are typical features of stems.
For example, cocoyam has corms, ginger has rhizomes, and Irish potatoes have tubers.
Hence, all three are correctly grouped as underground stems.
Answer:A. underground stems