The correct option is D Gametophyte reproduction
Gametophytes of mosses bear antheridia and female archegonia that form sperm cells and egg respectively. Fertilization of these haploid gametes produces a diploid zygote that divides mitotically to produce a multicellular embryo. The embryo finally develops into the mature sporophyte. Sporophyte of mosses reproduces asexually by haploid spores that germinate to form haploid gametophyte. Thus, the correct answer is D.