Final answer:
In Pteridophytes, the dominant life cycle phase is the sporophyte, which is more pronounced, free-living, and performs essential functions like photosynthesis.
Step-by-step explanation:
The dominant life cycle phase in Pteridophytes is the sporophyte. Pteridophytes, which include ferns, have a life cycle that involves an alternation of generations between the multicellular haploid gametophyte and the multicellular diploid sporophyte. While both stages are free-living, the sporophyte phase is longer-lasting, larger, typically green, and is the more recognizable part of the plant, carrying out photosynthesis and supporting the smaller gametophyte.
Owing to evolutionary processes, there has been a progression throughout plant history toward greater dominance of the sporophyte phase. The sporophyte in Pteridophytes, as seen in Figure 26.8 of many textbooks, is the phase that deals with dispersion and survival through the process of producing spores that will eventually grow into gametophytes. This evolutionary trend has led to the gametophyte phase becoming less conspicuous and typically shorter in duration, as the sporophyte phase takes on more central roles in structure, reproduction, and ecological interaction.
It is also essential to understand that both the gametophyte and sporophyte stages are multicellular, as stated in point (d), but the sporophyte is the 2n plant (point b) that has a more prominent role in the life cycle of Pteridophytes, contrary to mosses where the gametophyte takes center stage.