Wood is $.....................$

Cork cambium is a:

In cambium,the amount of secondary xylem produced is more than secondary phloem because..........

The activity of cambium in plants is under the control of

In dicot roots,cork cambium is derived from

During secondary growth of plants,stem phellogen cuts off cells on both sides. The outer cells get differentiated into ...$A$... and the inner cells get differentiated into ...$B$... cortex.
Choose the correct combination of $A$ and $B$ with reference to the above statement.