Final answer:
The statements that ferns and flowering plants produce spores and that both a tree and a large fern are diploid sporophytes are true. The statement that only ferns have a gametophyte is false, as flowering plants also have gametophytes. Only flowering plants produce pollen grains.
Step-by-step explanation:
The statement "Both ferns and flowering plants produce spores at some point in their life cycles" is true. Both types of plants indeed have a sporophyte stage that produces spores. For ferns, spores develop into a haploid gametophyte, which is free-living and produces gametes, leading to the development of a diploid sporophyte after fertilization. Contrastingly, flowering plants have a dominant sporophyte stage, and spores develop into gametophytes within the flowers. The statement "Only ferns have a gametophyte as part of their life cycle" is false, as flowering plants also have a gametophyte stage, albeit greatly reduced and not free-living like in ferns. For flowering plants, they produce distinct male gametophytes known as pollen grains. The statement "Only flowering plants produce pollen grains" is true. Finally, the statement "Both a tree and a large fern plant are diploid sporophytes" is also true. Trees, like all seed plants, and large ferns represent the sporophyte stage of their respective life cycles, which is diploid.