A vascular bundle without pith is

Write the precise function of

$(a)$ Sieve tube

$(b)$ Interfascicular cambium

$(c)$ Collenchyma

$(d)$ Aerenchyma

Abundant pith is characteristic of

The transverse section of a plant material shows the following anatomical features, $(a)$ the vascular bundles are conjoint, scattered and surrounded by clerenchymatous undle sheaths $(b)$ phloem parenchyma is absent. What will you identify it as?

Distinguish between the following : Stele and vascular bundle.