Final answer:
Herbaceous stems are described as soft, with xylem and phloem forming clusters of vascular bundles. Unlike woody plants, they do not have vascular tissue arranged in rigid growth rings.
Step-by-step explanation:
The correct description of herbaceous stems is 'Soft stems with clusters of xylem and phloem'. This is true because whereas woody plants have stems with vascular tissue arranged in concentric circles forming growth rings, herbaceous plants generally have more flexible, soft stems. Their vascular bundles consisting of xylem and phloem are not organized in such a rigid structure and hence, they do not produce the growth rings typical of woody stems. In dicot stems, the vascular bundles are arranged in a ring, but in monocot stems, the bundles are randomly scattered. Since the question does not specify monocots or dicots, the best general answer without that knowledge is soft stems with clusters of xylem and phloem as it can apply broadly to herbaceous plants.