**Core Concept**
Antibiotic use in lactating mothers requires careful consideration to minimize risks to the infant. Certain antibiotics can be secreted in breast milk and potentially cause adverse effects in the nursing infant.

**Why the Correct Answer is Right**
The correct answer is C. Erythromycin is a macrolide antibiotic that is generally considered safe for use during lactation. It is often recommended for treating bacterial infections in lactating mothers, as it has a low risk of causing adverse effects in the infant. In contrast, tetracyclines (A), sulfonamides (B), and aminoglycosides (D) are not recommended for use in lactating mothers due to their potential to cause adverse effects in the infant.

**Why Each Wrong Option is Incorrect**
**Option A:** Tetracyclines can chelate calcium ions and cause tooth discoloration and inhibition of bone growth in the infant.
**Option B:** Sulfonamides can displace bilirubin from albumin, increasing the risk of kernicterus in the infant.
**Option D:** Aminoglycosides can cause nephrotoxicity and ototoxicity in the infant.

**Clinical Pearl / High-Yield Fact**
When prescribing antibiotics to lactating mothers, it's essential to consider the potential risks to the infant and choose an antibiotic that has a low risk of causing adverse effects.

**Correct Answer:** C. Erythromycin