Which of the following is an example of alternation of generations?
1. A grandparent and grandchild each have dark hair, but the parent has blond hair.
2. A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
3. A diploid animal produces gametes by meiosis, and the gametes undergo fertilization to produce a diploid zygote.
4. A haploid mushroom produces gametes by mitosis, and the gametes undergo fertilization, which is immediately followed by meiosis