The correct option is D Secondary xylem
Tyloses are the outgrowths protruding from the parenchyma cells of xylem vessels. It generally protects the vascular tissue during stress like drought or infection. During unfavourable conditions, it falls from the sides of the cells and dam up the vascular tissue to prevent further damage to the plant. It can be traced in the secondary xylem. It aids in the process of converting sapwood into heartwood in some hardwood trees, especially in trees with larger vessels. These blockages can be used in addition to gum plugs as soon as vessels become filled with air bubbles, and they help to form a stronger heartwood by slowing the progress of rot.
Thus, the correct answer is option D.