Radial vascular bundles are found in

Radial vascular bundles are primarily found in the roots of plants. In these roots, the vascular tissue—comprising xylem and phloem—is arranged in a star-like pattern, with xylem at the center and phloem between the arms of the xylem. This arrangement facilitates the efficient transport of water, minerals, and nutrients from the soil to the rest of the plant.

In contrast, stems and leaves typically feature vascular bundles arranged in a ring or scattered pattern, not radially. Therefore, the correct answer is: a) roots