The correct answer is the (d.) rhizome. A rhizome is a horizontal stem at or just beneath the surface of the ground in which can give side to the roots and stems. It puts the lateral shoots of roots at intervals.
Rhizome: A horizontal stem at or just beneath the surface of the ground which can give rise to aerial stems, roots, or to more rhizome tissue. Rhizomes are a principal means of asexual reproduction in many plants.
