The correct option is B absence of root hairs
Root has four main regions - root cap, region of meristematic activity, region of elongation and region of maturation.
Root cap is the region of the root which covers the root apex. It is a thimble-like structure that protects the tender apex of the root as it makes its way through the soil. For water absorption by roots, fine and delicate thread-like structures called root hairs are needed. The root hairs are present only in the region of maturation of the root. Just below this region lies the region of elongation which is responsible for the growth of the root in length. Hence, due to absence of root hairs in the root cap region, water can not be absorbed by the root cap.