In fetal circulation, blood bypasses the lungs by flowing through the

A. Ductus venosus and ductus arteriosus: The ductus venosus bypasses the liver, not the lungs. The ductus arteriosus does allow blood to bypass the lungs by connecting the pulmonary artery to the aorta. However, this option is not entirely correct since the ductus venosus is not involved in bypassing the lungs.

B. Foramen ovale and ductus arteriosus: The foramen ovale allows blood to pass directly from the right atrium to the left atrium, bypassing the lungs. The ductus arteriosus connects the pulmonary artery to the aorta, also bypassing the lungs.

C. Fossa ovalis and umbilical arteries and vein: The fossa ovalis is a remnant of the foramen ovale in adults and does not function in fetal circulation. The umbilical arteries and vein are involved in exchanging oxygenated and deoxygenated blood between the fetus and placenta, not bypassing the lungs.

D. Ligamentum venosum and ligamentum arteriosum: These are the adult remnants of the ductus venosus and ductus arteriosus, respectively. They do not play a role in fetal circulation.

A. Lactose is a sugar in breast milk and is not the only source of nutrition during the first 2-3 days postpartum.

B. Casein is a protein found in breast milk but not the sole source of nutrition for the infant.

C. Colostrum is the nutrient-rich first milk produced by the mother in the first 2-3 days postpartum and provides essential nutrients and antibodies to the newborn.

D. Meconium is the infant's first stool and not a source of nutrition.