The correct option is C Potato
The underground stem lies below the surface of the soil. They are non-green, store food and take part in perennation. They bear buds and roots. Tuber is an oval or spherical underground swollen stem structure modified for food storage. It does not bear adventitious roots. For example - potato.
Sweet potato and carrot are modified roots which grow underground.
Groundnut is a leguminous crop which is known for its edible seeds.