The correct option is B Parenchyma
Pith is a central part of the ground tissue generally made up of parenchyma. It is present in the central portion of the stem. The cells which comprise pith are rounded in shape. They have large intercellular spaces. The cells of pith present between the vascular bundles constitute the pith rays, also called medullary rays. These parenchymatous cells are radially arranged in between the bundles and give the appearance of rays. The pith rays help in the radial conduction of food.