In the context of plant anatomy, xylem and phloem are two types of vascular tissues that are responsible for transporting water, nutrients, and other substances throughout the plant. When xylem and phloem are arranged in the same radius, it forms an avascular bundle.

Option 1: Collateral - This term describes the arrangement of xylem and phloem in a single radius. It is the correct answer because it aligns with the given description.

Option 2: Bicollateral - This term refers to the arrangement of xylem and phloem in two distinct radii. It does not match the given description, so it is not the correct answer.

Option 3: Concentric - This term describes the arrangement of xylem and phloem in concentric circles. It does not align with the given description, so it is not the correct answer.

Option 4: Radial - This term generally refers to any arrangement that occurs in a radial pattern. While it is a plausible answer, option 1, collateral, aligns better with the given description. Therefore, option 4 is not the correct answer.

In summary, when xylem and phloem are arranged in the same radius, it