Final answer:
The decidua basalis and the chorionic villi combine to form the placenta, which connects the mother to the fetus for nutrient and waste exchange. The answer is option C.
Step-by-step explanation:
The decidua basalis of the endometrium and the chorionic villi of the fetus grow together to form the placenta. The maternal portion of the placenta develops from the decidua basalis. Meanwhile, the chorionic villi are part of the chorion, a membrane that forms the fetal portion of the placenta. The chorionic villi burrow into the endometrium, resembling tree roots, and assist in forming the connection between the mother and the developing fetus, facilitating the exchange of nutrients and waste.
To more directly answer the question, the decidua basalis of the endometrium and the chorionic villi of the fetus grow together to form the c. placenta.