“Sap wood” is otherwise called

The heartwood cannot conduct water because of

Assertion : In woody stems, the amount of heart wood continues to increase year after year.
Reason : The cambial activity continues uninterrupted

Identify the correct statements:

$A$. Lenticels are the lens-shaped openings permitting the exchange of gases.

$B$. Bark formed early in the season is called hard bark.

$C$. Bark is a technical term that refers to all tissues exterior to vascular cambium.

$D$. Bark refers to periderm and secondary phloem.

$E$. Phellogen is single-layered in thickness.

Choose the correct answer from the options given below:

Give explantion about heartwood and sap wood.