The correct option is C Pteridophyta
Most conspicuous alternation of generation occurs in Pteridophyta. This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus, which produces gametes). Pteridophytes differ from mosses and seed plants in that both generations are independent and free-living, although the sporophyte is generally much larger and more conspicuous. Hence option C is correct.