Nitrate (NO₃^-) Must Be Reduced to the Level of Ammonia

Nitrate (NO₃^-) must be reduced to the level of ammonia (NH₃) in leaves to be assimilated into amino acids. Which statement best describes the transport of nitrate and amino acids in plants?

A) Nitrate enters the phloem in the roots and is transported to the leaves. Amino acids are transported to the rest of the plant by the phloem.
B) Nitrate enters the xylem in roots by an entirely apoplastic route and is transported to the leaves. Amino acids are transported in the phloem.
C) Nitrate enters the xylem in roots by a pathway that includes its transport across at least one plasma membrane and is transported to the leaves. Amino acids are transported in the phloem.
D) Nitrate enters the xylem in roots by a pathway that includes its transport across at least one plasma membrane and is transported to the leaves. Amino acids are transported in the xylem.
E) The nitrate concentration in phloem sap would be higher than that in xylem sap.