Final answer:
The decidua basalis of the endometrium and the chorionic villi of the fetus together form the placenta, which supports fetal development by facilitating nutrient and waste exchange. Therefore correct option is C
Step-by-step explanation:
The decidua basalis of the endometrium and the chorionic villi of the fetus grow together to form the placenta. This organ is crucial for fetal development as it facilitates the exchange of oxygen, nutrients, and wastes between the mother and the fetus. The maternal portion of the placenta develops from the decidua basalis, and the fetal portion, which includes the chorionic villi, emerges from the trophoblast cells. These villi invade the maternal endometrium to ensure a stable and efficient connection between the mother and the developing embryo/fetus.