Concept:Alternation of generation is a life cycle alternating between haploid gametophyte and diploid sporophyte stages.Explanation:Mosses clearly show alternating gametophyte and sporophyte generations in their life cycle.The gametophyte is the dominant green plant body, while the sporophyte grows on it and produces spores.Fungi, grasses, and conifers do not exhibit this as their main distinguishing feature.Answer:A. mosses