The vascular cambium is ..........

Wood is

In old trees,the greater part of secondary xylem is dark brown and resistant to insect attack due to:
$(a)$ secretion of secondary metabolites and their deposition in the lumen of vessels.
$(b)$ deposition of organic compounds like tannins and resins in the central layers of stem.
$(c)$ deposition of suberin and aromatic substances in the outer layer of stem.
$(d)$ deposition of tannins,gum,resin and aromatic substances in the peripheral layers of stem.
$(e)$ presence of parenchyma cells,functionally active xylem elements and essential oils.
Choose the correct answer from the options given below:

Identify the correct order of the components with reference to their arrangement from outer side to inner side in a woody dicot stem.
$I.$ Secondary cortex
$II.$ Autumn wood
$III.$ Secondary phloem
$IV.$ Phellem

In any dicot root having secondary growth,the cork is the

Secondary growth is absent in