Which of the following is haploid?

The correct option is B Secondary spermatocytes and secondary oocytes
Gametogenesis involves meiosis, which occurs in two stages - meiosis I, which is reductional and meiosis II, which is equational. Primary spermatocytes undergo meiosis I to produce haploid secondary spermatocytes. The secondary spermatocytes will undergo meiosis II to produce spermatids, which will be ultimately transformed to spermatozoa. Similarly, primary oocytes will undergo meiosis I to produce haploid secondary oocytes. This division is asymmetrical and a tiny polar body is also produced. The secondary oocyte will undergo meiosis II just before fertilization to form the ovum which will fertilize with the male gamete.