Final answer:
Option B) A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte), is an example of alternation of generations in plants.
Step-by-step explanation:
Alternation of generations is a reproductive strategy exhibited by plants, and an example of this is option B) A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte). In this process, the diploid sporophyte undergoes meiosis to produce spores, which then develop into multicellular haploid gametophytes.