The correct option is D Sweet potato - stem
The potato that we consume is a modified underground stem of the potato plant. Hence, the edible part of a potato plant is its stem. But in sweet potatoes, the roots are modified to store food and are edible. Therefore, the edible part of sweet potatoes are roots. Similarly, food is stored in the roots of carrots, and hence the edible part of the carrot plant is its roots. Leaves act as the unit of storage in spinach, and hence leaves are the edible part of spinach plants.