The correct answer is option 2: Placenta. The placenta is an organ that forms during pregnancy and acts as a connection between the mother and the developing fetus. It provides essential nutrients and oxygen to the fetus while removing waste products. The placenta is attached to the wall of the uterus and contains blood vessels that allow for the transfer of nutrients, gases, and waste products. This ensures that the developing fetus receives all the necessary nutrients for growth and development. The uterus, option 1, is the organ where the fetus grows and is protected during pregnancy, but it does not directly supply food to the fetus. The ovary, option 3, produces eggs but is not involved in providing nutrients to the developing fetus. The allantosis, option 4, is a membrane that is present in the embryos of reptiles, birds, and mammals, but it does not supply food to the fetus in humans.