A nurse is caring for an infant who has a congenital heart defect. Which of the following defects is associated with increased pulmonary blood flow?

The correct answer is C: Patent ductus arteriosus. In this defect, the ductus arteriosus fails to close after birth, causing increased blood flow from the aorta to the pulmonary artery, leading to increased pulmonary blood flow. This results in pulmonary congestion and increased workload on the heart. Tetralogy of Fallot (choice A) involves decreased pulmonary blood flow due to a pulmonary stenosis. Tricuspid atresia (choice B) is a cyanotic defect with decreased pulmonary blood flow. Coarctation of the aorta (choice D) causes narrowing of the aorta, leading to increased systemic blood pressure but does not affect pulmonary blood flow.