Final answer:
The three classes of bryophytes are mosses, liverworts, and hornworts, and they are collectively characterized as nonvascular plants that require moist environments.
Correct option is a) Mosses, liverworts, and hornworts.
Step-by-step explanation:
The three classes of bryophytes are a) Mosses, liverworts, and hornworts. These are all nonvascular plants, which means they do not have a vascular system consisting of xylem and phloem like many other plants. Because of this, they are also generally small in size and require moist environments to survive.
Liverworts, or Marchantiophyta, are thought to be the plants most closely related to the earliest terrestrial plants. Hornworts, or Anthocerotophyta, are named for their horn-like sporophytes. Mosses, or true Bryophyta, are the largest group, with around 12,000 species, and they exhibit some adaptations, such as the development of stomata, which reflect evolutionary steps towards land plant life.