Why Do Vascular Plants Need Phloem? All Four of the Provided

Multiple Choice

Why do vascular plants need phloem? All four of the provided answers are correct. Select the answer that BEST explains the existence of phloem.

A) for chemical signaling between widely separated parts of the plant
B) because not all parts of the plant are independently autotrophic
C) to create a "return loop" for xylem flow back to the root
D) because diffusion is not efficient over long distances