**Core Concept**
Nonsteroidal anti-inflammatory drugs (NSAIDs) are a class of medications that can cause nephrotoxicity through various mechanisms, including inhibition of prostaglandin synthesis, reduction of renal blood flow, and direct tubular toxicity. Renal prostaglandins play a crucial role in maintaining glomerular filtration rate (GFR) and renal blood flow.

**Why the Correct Answer is Right**
The least nephrotoxic option among the given choices is **C. Ibuprofen**. Ibuprofen, a non-selective NSAID, has a relatively lower risk of nephrotoxicity compared to other NSAIDs. This is due to its lower potency and shorter duration of action, which reduces the risk of renal vasoconstriction and prostaglandin inhibition. Additionally, ibuprofen has a more favorable pharmacokinetic profile, with a higher clearance rate and lower peak plasma concentration, which further minimizes its nephrotoxic potential.

**Why Each Wrong Option is Incorrect**
* **Option A:** Indomethacin is a potent NSAID with a high risk of nephrotoxicity, particularly in patients with pre-existing renal disease or those taking other nephrotoxic medications. Its potent inhibition of prostaglandin synthesis can lead to significant reductions in GFR and renal blood flow.
* **Option B:** Diclofenac is another high-risk NSAID, known for its potential to cause renal impairment, particularly in patients with hypertension, heart failure, or those taking diuretics. Its long half-life and high peak plasma concentration increase the risk of nephrotoxicity.
* **Option D:** Ketorolac is a potent NSAID with a high risk of nephrotoxicity, particularly in patients with pre-existing renal disease or those taking other nephrotoxic medications. Its potent inhibition of prostaglandin synthesis can lead to significant reductions in GFR and renal blood flow.

**Clinical Pearl / High-Yield Fact**
When prescribing NSAIDs, it is essential to consider the patient's renal function, cardiovascular status, and the presence of other nephrotoxic medications to minimize the risk of nephrotoxicity. Patients with pre-existing renal disease or those taking other nephrotoxic medications should be closely monitored for signs of nephrotoxicity, such as decreased urine output, hypertension, and elevated serum creatinine levels.

**Correct Answer:** C. Ibuprofen