Almost Immediately After a Young Leaf Primordium First Begins to Bulge

Almost immediately after a young leaf primordium first begins to bulge out ____.

A) undifferentiated vascular tissues that will later become xylem and phloem penetrate it
B) small xylem vessels penetrate it first, followed soon after by phloem
C) small phloem vessels penetrate it first, followed soon after by xylem
D) small xylem and phloem vessels penetrate it together
E) specialized vascular tissue cells penetrate and soon differentiate into phloem or xylem vessels