Final answer:
A seed with one cotyledon is classified as a Monocot. Leaf veins are classified under Leaf Structures, while a stem with vascular bundles arranged in a ring and flowers with parts in fours or fives pertain to Eudicots.
Step-by-step explanation:
A seed with one cotyledon belongs to the category of Monocots. The veins on a leaf belong to the category of Leaf Structures. A stem with vascular bundles arranged in a ring belongs to the category of Eudicots (also known as Dicots). The floral part of a flower belongs to the category of Eudicots when the flower parts come in fours or fives.