**Core Concept**
The question is testing the safety of medications in lactating mothers, specifically their excretion in breast milk and potential effects on the infant. This concept is crucial in clinical practice, as many medications are excreted in breast milk and can have varying effects on the infant.

**Why the Correct Answer is Right**
The correct answer is a medication that is considered safe for use in lactating mothers, typically because it is not significantly excreted in breast milk or has a minimal risk of causing harm to the infant. The safety of medications in lactating mothers is evaluated based on the medication's pharmacokinetics, including its lipid solubility, protein binding, and renal clearance. Medications with a low lipid solubility and high protein binding are less likely to be excreted in breast milk.

**Why Each Wrong Option is Incorrect**
**Option A:** This medication is a beta-lactam antibiotic and is known to be excreted in breast milk. Its use in lactating mothers is generally avoided due to the risk of gastrointestinal side effects in the infant.
**Option B:** This medication is a macrolide antibiotic and can be excreted in breast milk, although its effects on the infant are generally minimal. However, it is still not considered a safe option for use in lactating mothers.
**Option C:** This medication is a nonsteroidal anti-inflammatory drug (NSAID) and is known to be excreted in breast milk. Its use in lactating mothers is generally avoided due to the risk of gastrointestinal side effects in the infant.

**Clinical Pearl / High-Yield Fact**
When considering the use of medications in lactating mothers, it is essential to evaluate the medication's safety profile, including its excretion in breast milk and potential effects on the infant. The American Academy of Pediatrics (AAP) and other reputable sources provide guidelines for the safe use of medications in lactating mothers.

**Correct Answer:** D.