Which of the Following Characteristics Is Unique to Plant Hormones

Which of the following characteristics is unique to plant hormones?

A) Plant hormones may be bound by intracellular steroid receptors.
B) Plant hormones may be delivered to target cells through a vascular system.
C) Plant hormones may be delivered to target cells through the air.
D) The target cells for plant hormones may be located large distances from the cells that produce and secrete the hormones.