**Core Concept**
The patent ductus arteriosus (PDA) is a congenital heart defect characterized by the failure of the ductus arteriosus to close after birth. In premature infants, this can lead to excessive pulmonary blood flow, respiratory distress, and potential complications. Closure of the PDA is crucial for the infant's health.

**Why the Correct Answer is Right**
Indomethacin is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits the production of prostaglandins, which are key mediators in the maintenance of the ductus arteriosus. Prostaglandins cause the ductus arteriosus to remain patent by promoting vasodilation and inhibiting platelet aggregation. By administering indomethacin, the production of prostaglandins is decreased, leading to the closure of the ductus arteriosus. This is the primary mechanism by which indomethacin stimulates closure of the PDA.

**Why Each Wrong Option is Incorrect**
**Option A:** Ibuprofen is another NSAID that can be used to close a PDA, but it is not the most commonly used or recommended medication for this purpose.
**Option B:** Furosemide is a diuretic that is used to treat fluid overload, but it is not directly involved in the closure of the PDA.
**Option C:** This option is blank, so it cannot be evaluated.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the closure of the PDA is a critical step in the management of premature infants with this condition. Indomethacin is the first-line treatment for PDA closure, and its administration should be carefully monitored to avoid potential side effects.

**Correct Answer:** A. Indomethacin.