The correct option is D Assertion is incorrect but Reason is correct.
Protophloem is the first formed phloem which has thin walled cells. It is formed from procambium. Therefore, assertion is incorrect.
During secondary growth the vascular cambium gives rise to xylem and phloem cells. There are different types of arrangement of xylem and phloem. One of such arrangement is amphivasal, in which the phloem is in the center and xylem surrounds it from all sides. Therefore, reason is correct.
Thus, the correct answer is option D.