In botany,from the perspective of evolution and phylogeny,which plant structure can be used to represent changes?

Read the following four statements $(A-D)$:
$(A)$ Both photophosphorylation and oxidative phosphorylation involve uphill transport of protons across the membrane.
$(B)$ In dicot stems,a new cambium originates from cells of pericycle at the time of secondary growth.
$(C)$ Stamens in flowers of Gloriosa and Petunia are polyandrous.
$(D)$ Symbiotic nitrogen fixers occur in free-living state also in soil.
How many of the above statements are right?

$T.S.$ of a dicot leaf is given below. Certain parts have been indicated by alphabets. Choose the correct option.

$A$ : Bast fibres are collenchymatous fibres.
$R$ : Fibres are absent in secondary phloem.

Distinguish between the following: Protoxylem and metaxylem.

The branch of botany that deals with the internal study of plants is called .........