**Core Concept**
In renal failure, the choice of medication is crucial due to altered pharmacokinetics and pharmacodynamics. The kidneys play a significant role in drug elimination, and impaired renal function can lead to drug accumulation and toxicity.

**Why the Correct Answer is Right**
Furosemide (Option C) can be given safely in renal failure because it is primarily excreted unchanged in the urine. Although its clearance is reduced in patients with renal impairment, the dose can be adjusted to maintain its diuretic effect. Additionally, furosemide has a relatively low toxicity profile, making it a safer choice in this setting.

**Why Each Wrong Option is Incorrect**
**Option A:** Aminoglycosides (e.g., gentamicin) are nephrotoxic and can exacerbate renal failure. Their use in patients with renal impairment is generally contraindicated due to the risk of further kidney damage.
**Option B:** Lithium is primarily excreted by the kidneys and has a narrow therapeutic index. Its use in patients with renal failure can lead to lithium toxicity, which can be fatal.

**Clinical Pearl / High-Yield Fact**
In patients with renal failure, it's essential to choose medications that are either renally cleared or have a long elimination half-life, allowing for dose adjustments and minimizing the risk of toxicity.

**Correct Answer:** C. Furosemide.