Final answer:
The correct option is a) Gametophyte cells are multicellular. The gametophyte is the haploid stage in the life cycle of plants and in ferns, it is a multicellular structure that produces archegonia and antheridia.
Step-by-step explanation:
The correct option is a) Gametophyte cells are multicellular. The gametophyte is the haploid stage in the life cycle of plants, where gametes are produced. In ferns, the gametophyte is a multicellular structure that produces archegonia and antheridia, which contain the eggs and sperm, respectively. This is different from the sporophyte, which is the diploid stage and produces haploid spores by meiosis.