The correct option is D Sieve tubes in winter
Callose blocks sieve tubes in winter. It is a plant polysaccharide. It is composed of glucose residues linked together through -1,3-linkages and is termed a -glucan. It is thought to be manufactured at the cell wall by callose synthases. Deposits often appear on the sieve plates at the end of the growing season. Callose also forms immediately around the developing meiocytes and tetrads of sexually reproducing angiosperms.
Therefore, the correct answer is option D.