The cortex of a herbaceous stem is primarily composed of parenchyma cells, which are large and thin-walled, often used for food storage or photosynthesis. The outer region of the cortex, just below the epidermis, typically contains layers of collenchyma cells, which have unevenly thickened cell walls and provide flexible mechanical support to the growing stem without hindering growth.

A. sclerenchyma and collenchyma: While collenchyma is present, sclerenchyma cells are generally dead at maturity and non-stretchable. They are usually found in mature, non-growing regions or associated with vascular bundles, and are less common in the primary cortex of a typical herbaceous stem.

B. collenchyma and xylem: Xylem is part of the vascular tissue system, located in the central cylinder (stele), not the cortex (which is the region between the epidermis and vascular bundles).

C. Sclerenchyma and parenchyma: As mentioned above, sclerenchyma is generally not a primary component of the herbaceous stem cortex, which requires flexibility for growth.