**Core Concept**
The question is testing the student's knowledge of antibacterial agents that can cause significant side effects, specifically ototoxicity (damage to the ear) and nephrotoxicity (damage to the kidneys). This is a critical aspect of pharmacology in clinical practice.

**Why the Correct Answer is Right**
Aminoglycosides, such as gentamicin, are a class of antibacterial agents that can cause both ototoxicity and nephrotoxicity. This is due to their mechanism of action, which involves binding to the bacterial 30S ribosomal subunit, inhibiting protein synthesis, and causing cell death. However, aminoglycosides can also enter human cells, particularly renal cells and hair cells in the inner ear, where they can cause damage and lead to ototoxicity and nephrotoxicity. The risk of ototoxicity is increased with high doses, prolonged therapy, and pre-existing hearing loss.

**Why Each Wrong Option is Incorrect**
* **Option A:** Cephalosporins are a class of beta-lactam antibiotics that are generally well-tolerated and do not cause ototoxicity or nephrotoxicity.
* **Option B:** Macrolides, such as erythromycin, are a class of antibiotics that are primarily associated with gastrointestinal side effects, such as nausea and vomiting, rather than ototoxicity or nephrotoxicity.
* **Option D:** Fluoroquinolones, such as ciprofloxacin, can cause various side effects, including tendonitis and QT interval prolongation, but are not typically associated with ototoxicity or nephrotoxicity.

**Clinical Pearl / High-Yield Fact**
Aminoglycosides should be used with caution in patients with pre-existing hearing loss or kidney disease, and their use should be limited to the minimum necessary to achieve therapeutic levels.

**Correct Answer:** C. Aminoglycosides.