Final answer:
Secondary spermatocytes each contain 23 chromosomes with duplicate chromatids, which is the result of primary spermatocytes undergoing meiosis I.
Step-by-step explanation:
The question is focused on the stage of spermatogenesis involving secondary spermatocytes. During the process of spermatogenesis, the diploid spermatogonia undergo mitosis to form primary spermatocytes that also are diploid, meaning they have a full set of 46 chromosomes. These primary spermatocytes then go through meiosis I to produce two secondary spermatocytes, each with 23 chromosomes. Importantly, each of these chromosomes still consists of a pair of duplicate chromatids. Following this, the secondary spermatocytes undergo meiosis II, where the chromatids are separated, eventually resulting in haploid spermatids with 23 single chromosomes.
Therefore, secondary spermatocytes each contain 23 chromosomes, each with a pair of duplicate chromatids, making option A the correct answer to the question.