Bark refers to all tissues exterior to the

$A$ : Oldest layer of sapwood lies just outside vascular cambium.

$R$ : Sapwood contains actively conducting vessels and occupies central part of stem.

$I.$ Protection of internal tissues

$II.$ Protection of leaves from microbes

$III.$ Gaseous exchange

$IV.$ Reduction in the rate of transpiration through epidermal cells due to trichomes

Which of the function of epidermis is/are relevant from the above given statements?

What is the position of oldest secondary phloem?

Choose incorrect sentence :

The functional xylem of dicot tree is