Final answer:
Bryophytes, like mosses, are unique among plants in that they do not produce flowers, using spores and flagellated sperm for reproduction with the gametophyte as the dominant life cycle stage. Therefore, the most appropriate correct option is C.
Step-by-step explanation:
Most bryophytes, such as mosses, differ from other plants in that they do not produce flowers. Unlike angiosperms which reproduce through flowers and seeds, bryophytes utilize spores for reproduction. While many plants produce spores, mosses also have a distinctive reproductive strategy which involves flagellated sperm that swim to reach the egg, hence requiring a moist environment for successful fertilization. The life cycle of bryophytes is dominated by the gametophyte stage, contrary to other plants where the sporophyte stage is usually prominent. The other options listed (such as producing spores, and lacking true leaves and roots) are not unique to bryophytes, as other plant groups like ferns also share these characteristics. Additionally, bryophytes do not have cones; that is a feature of gymnosperms, which do produce seeds, unlike bryophytes.