This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sex Hormones, Subject name: Physiology
[{'content': 'Successful fertilization is most likely to occur when the oocyte is in: \nSelect and explain. \nA. The oviduct and has entered the second meiotic division, B. The uterus and has completed the first meiotic division, C. Metaphase of mitosis, D. The graafian follicle, which then enters the oviduct', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. The oviduct and has entered the second meiotic divisionFertilization occurs in the oviduct. The oocyte must have entered a second meiotic division to reduce the chromosome number of the oocyte to a haploid state (n) so that it may fuse with the sperm (also haploid), producing a 2n zygote. Fertilization does not occur in the uterus, especially not after the first meiotic division when the chromosome number is 2n. In the adult ovary, oocytes do not undergo mitosis. Graafian follicles do not enter the oviduct and are not fertilized. Fertilization does not occur in the uterus, and the oocyte does not implant. The blastocyst will implant in the uterus. In addition, extrusion of the polar body is associated with fertilization, but this event occurs within the oviduct.', 'role': 'assistant'}]