How many of the following are haploid?

Primary oocyte, primary spermatocyte, secondary oocyte, spermatids, ova, secondary spermatocyte.

The correct option is C Four
The formation of gametes is called gametogenesis. The gametes, sperm and ova contain a haploid number of chromosomes.

In males, spermatogonia (diploid) multiplies by mitosis to form primary spermatocyte (diploid). The primary spermatocyte undergoes meiosis I to form two secondary spermatocytes. The first meiotic division is reduction division, so each of the two cells contains a haploid number of chromosomes. These secondary spermatocytes undergo meiosis II to give rise to four spermatids (haploid). The second meiotic division is equational division, so the same number of chromosomes are maintained in the products. Then spermatids mature into sperm.

In females, oogonia(diploid) gives rise to the primary oocyte ( diploid)which undergoes meiosis I and results in the secondary oocytes and one polar body. Both have a haploid number of chromosomes. Each of the secondary oocytes undergoes meiosis II to form an ovum (haploid) and secondary polar body (haploid).
Primary oocyte and primary spermatocyte are diploid, each with 46 chromosomes.
Secondary oocyte, ova, secondary spermatocyte and spermatids are haploid in number, each with 23 chromosomes.