Correct option is D
Pith:
It is the innermost part of tree consisting of cellular tissue which is used for nourishment of tree in young age.
Heartwood:
The inner annual rings surrounding the pith are known as heartwood. It imparts rigidity to the tree.
Cambium Layer:
It is a thin layer of sap between sapwood and the inner bark.
Inner bark:
It gives protection to the cambium layer.
Outer bark:
It is the outermost part of the tree.
