Which of the following occurs in the placenta?

The correct choice highlights a fundamental function of the placenta, which is the crucial nutrient and waste exchange between the mother and fetus. Throughout pregnancy, the placenta acts as an interface, allowing nutrients, oxygen, and antibodies from the mother's blood to pass to the fetus while simultaneously facilitating the transfer of waste products from the fetus back to the mother's circulation for disposal. This exchange is vital for ensuring the developing fetus receives the necessary elements for growth and development while maintaining proper waste management.

The other choices do not accurately describe the role of the placenta. The development of the fetus primarily occurs in the uterus, not within the placenta itself. Additionally, oxygen is not absorbed directly from the air by the fetus; instead, the fetus relies on the mother’s blood for oxygen, which is delivered through the placenta. Lastly, while the placenta does store some nutrients temporarily, its primary role is not as a storage unit but as an active participant in the metabolic processes that support fetal life.