In which of the following is the differentiation between heartwood and sapwood not observed?

$A$ : The oldest layer of sapwood lies just outside the vascular cambium.
$R$ : Sapwood contains actively conducting vessels and occupies the central part of the stem.

Growth rings $(annual\ rings)$ are formed by the activity of:

Diffused porous woods are characteristic of plants growing in

Age of a tree can be estimated by

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$: Late wood has fewer xylary elements with narrow vessels.
Reason $R$: Cambium is less active in winters.
In the light of the above statements,choose the correct answer from the options given below: