The correct option is B Lenticels
Lenticels are raised pores found in the stem of a woody plant that allows gas exchange between the atmosphere and the internal tissues.
Stomata are also pores found on the underside of leaves that carry out similar function . Plants carry out gas exchange through these structures.
Vascular system that involves xylem and phloem help in the transportation of substances.
Mesophyll cells are found in leaves and are specialised for photosynthesis.