The correct option is
B Sugar transport
Boron is a micronutrient required by the plant in a small amount. It is absorbed by the plant in the form of Boron ions. It is required for uptake and utilization of Ca+. It is necessary for membrane functioning, pollen germination, cell elongation and cell differentiation. It is also required for sugar translocation through the phloem.
So the correct is 'Sugar transport'.