Correct Answer: D

Rationale: The correct answer is D: Patent ductus arteriosus. This defect leads to increased pulmonary blood flow because the ductus arteriosus, a fetal blood vessel connecting the pulmonary artery and aorta, remains open after birth, allowing blood to flow back into the pulmonary circulation. This results in increased blood volume in the lungs.

A: Coarctation of the aorta is a narrowing of the aorta, leading to decreased blood flow to the lower part of the body, not increased pulmonary blood flow.
B: Pulmonary atresia is a condition where the pulmonary valve is not formed properly, leading to decreased blood flow to the lungs, not increased.
C: Tetralogy of Fallot involves a combination of defects leading to decreased pulmonary blood flow.

Therefore, the correct answer is D as it is the only one associated with increased pulmonary blood flow.

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