The answer would be: A. gametes
Option B would not be the answer because ovaries is apart of the female reproduction system where egg cells are produced, not sex cells.
Option C is also not the answer since a zygote is formed from both male and female sex cells. However, it may be formed by the two but it still doesn't make it a sex cell.
Option A however is the correct answer since gametes is another word used for sex cells.
Hope this helps! :3