Final answer:
Gametes are produced by meiosis in both humans and land plants. Humans employ a diploid-dominant life-cycle where the only haploid cells produced are the gametes.
Step-by-step explanation:
The correct statement among the given options is 'A. Gametes are produced by meiosis in humans and land plants.' In humans and nearly all animals, a diploid-dominant life-cycle strategy is employed, wherein the only haploid cells produced by the organism are the gametes. This is done through the process of meiosis by specialized diploid cells called germ cells.
On the other hand, in land plants, we see a lifecycle involving alternation of generations. Here, the diploid sporophyte phase and haploid gametophyte phase alternate. The haploid gametes are produced by the gametophyte through mitosis since the organism is already haploid. However, the diploid sporophyte is produced by the fusion of these haploid gametes, restoring the diploid state. Here, specialized cells of the diploid sporophyte will undergo meiosis, producing haploid spores to start the cycle anew.
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