Nutrients and oxygen are transferred from a mother to her developing fetus through the

A) embryo.
B) ovaries.
C) teratogens.
D) placenta.

The placenta is the organ that connects the developing fetus to the uterine wall and allows for the transfer of nutrients and oxygen from the mother to the fetus. The other answer choices are not relevant to this process - the embryo is the developing entity itself, the ovaries produce and release eggs but are not directly involved in fetal nourishment, and teratogens are substances that can cause birth defects but are not involved in the transfer of essential nutrients.