You find a plant unfamiliar to you and observe that it has vascular bundles scattered throughout the stem cross section. what do you conclude about the plant?

The plant is a monocot.

The plant is vascular so it could be a fern, gymnosperm or angiosperm.
In the stem cross section of the fern, the vascular tissue forming a non-complete cylinder is present. Gymnosperm has a stem similar to angiosperm. In the stem cross section wood rays are like the spokes of the wheel. Thus, it leaves the angiosperms. Among angiosperms, dicots have vascular bundles are organized as a ring, while monocots have vascular bundles scattered throughout the stem cross section.
Therefore, a found plant must be a monocot.