Fallopian tube
Explanation:
The female reproductive system consists of various organs that works together to bring about a successful reproductive process. These structures include the vagina, uterus/womb, fallopian tube and ovary as mentioned in the question. The ovary is the main female reproductive organ responsible for producing the egg/ovum.
The egg produced by the ovary is then fertilized by a sperm cell that enters the female reproductive tract through the vagina. This fertilization process occurs when the egg and sperm meet in the fallopian tube also called oviduct. Fallopian tube is like a passage for the egg.