That would be erosion. I know this because i spent years studying rocks and had straight passed all of it. Hope this helps. ;)
The aswer is b. Vascular Cambium
it is a plant tissue which is located between Xylem and Phloem in the stem and root of a vascular plant and the source that produces Secondary xlem and phloem
Nb : Vascular Cambium does not transport waters , minerals, it only produce Xylem and Phloem which add the tree's girth
