[Solved] What is the ratio of oxygen atoms to hydrogen atoms in the compound Fe<sub>4</sub>(PO<sub>4</sub>)<sub>3</sub>(OH)<sub>3</sub> •<sup> </sup>12H<sub>2</sub>O? A)15:3 B)27:15 C)27:27 D)18:27 E)25:17 Gymnosperms: A group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, characterized by their naked seeds not enclosed in an ovary. Angiosperms: A large group of plants characterized by having flowers and producing seeds enclosed within a fruit. Xylem: Complex vascular tissue of plants; cell walls of its dead tracheids and vessel elements form tubes that distribute water and mineral ions through the plant body. Tracheids: Component of xylem. Tapered cells that die when mature; pitted walls that remain interconnect with other tracheids to form water-conducting tubes.