As secondary growth proceeds in a tree,the thickness of which of the following increases?

When the vascular cambium is present between the xylem and phloem,then the vascular bundle is called,

The anatomy of springwood shows some peculiar features. Identify the correct set of statements about springwood.
$(a)$ It is also called as the earlywood
$(b)$ In spring season cambium produces xylem elements with narrow vessels
$(c)$ It is lighter in colour
$(d)$ The springwood along with autumnwood shows alternate concentric rings forming annual rings
$(e)$ It has lower density
Choose the correct answer from the options given below:

$A$ continuous ring of cambium is formed by:

What is the position of the oldest secondary phloem?

Describe the activity of the cambial ring.