Which of the Following Statements Describes an Example of Alternation

Which of the following statements describes an example of alternation of generations?

A) A grandparent and grandchild each have dark hair, but the parent has blond hair.
B) A diploid plant (sporophyte) produces a spore by meiosis that gives rise to a multicellular, haploid pollen grain (gametophyte) .
C) A diploid animal produces gametes by meiosis, and the gametes undergo fertilization to produce a diploid zygote.
D) A haploid mushroom produces gametes by mitosis, and the gametes undergo fertilization, which is immediately followed by meiosis.