Answer:
C (fertilization)
Step-by-step explanation:
ALTERNATION OF GENERATIONS is a vivid phenomenon in the life cycle of moss. The diploid sporophyte (2n) produces haploid spores (n), which develops into a bud called protonema that eventually grows into the haploid gametophyte (n).
The male gametophyte called ANTHERIDIUM produces the haploid (n) sperms/antherozoids while the female gametophyte called ARCHEGONIUM produces the haploid (n) egg. The sperm swims to the archegonium (female gametophyte) and fertilizes the egg. This fertilization process results in the formation of a diploid sporophyte (2n) i.e. sperm(n) + egg(n).
The sporophyte produces spores again and the cycle continues in that manner.