Identify the incorrect statement.

In old dicot stems,a major part of the wood is filled up with tannins,resins,gums,etc. This part of the wood is called:

Trees in desert regions .......

Select the wrong statements.
$I.$ Primary and secondary phloem gets crushed during secondary growth.
$II.$ During secondary growth,primary xylem remains more or less intact.

Which of the following is the function of heartwood?

$I.$ Annual rings are formed as a result of seasonal environmental conditions.
$II.$ Tracheids/vessel elements are larger during periods when water is abundant.
$III.$ Tracheids/vessel elements have thicker walls during periods of water deprivation.
$IV.$ Wood formed in previous years is always darker than newer wood.
Select the combination of correct statements from the options given below.