Which of the following allows a plant's vascular system to work as a transport system?

a a plant's vascular system is made up of specialized cells that move around the plant as it grows.

b a plants vascular system is made up of specialized cells that are covered in a thick cell wall.

c a plants vascular system is made up of specialized cells that for straw-like tubes.

d a plants vascular system is made up of specialized cells that divide as the plant grows.