Final answer:
Gymnosperms, according to the eukaryotic tree, are most closely related to Gnetophyta, a group known for its similarities to angiosperms.
Step-by-step explanation:
According to the eukaryotic tree, Gymnosperms are most closely related to the Gnetophyta group. Gnetophytes are considered the closest group to angiosperms (flowering plants) because they produce true xylem tissue that contains both tracheids and vessel elements, which are also found in angiosperms. While there is some debate among scientists, the current understanding is that Gnetophyta is the closest relative of Gymnosperms to angiosperms.