The correct option is B Chemotaxis
Chemotaxis is the movement of an organism or plant in response to a chemical stimulus. Somatic cells, bacteria and other single cell or multicellular organisms direct their movements according to certain chemicals in their environment. It is clearly seen in the case of growth of pollen tube towards the embryo sac. The pollen tube does not directly reach the ovary in a straight line. It travels near the skin of the style and curls to the bottom of the ovary, then near the receptacle, it breaks through the ovule through the micropyle and the pollen tube bursts into the embryo sac.