Okay, let's tackle this question. The patient had surgery for colonic carcinoma and now has a solitary liver nodule. The question is about the treatment of choice. First, I need to recall the management of liver metastases from colorectal cancer.

Colorectal cancer commonly metastasizes to the liver. When there's a solitary nodule, the treatment of choice is usually surgical resection if it's feasible. The options might include other treatments like chemotherapy, ablation, or maybe even no treatment. But the best option is surgery if possible because it can offer a chance for a cure.

So the correct answer is probably C, which is surgical resection. Let me check the options again. The user didn't list the options, but the correct answer is given as C. So the explanation should focus on why resection is the best. The other options might be things like systemic chemotherapy or radiation, which are less effective for solitary metastases. Also, ablation is an option but not the first-line. The key here is that resection is the treatment of choice when possible.

**Core Concept**
Colorectal cancer commonly metastasizes to the liver, and solitary hepatic metastases are best managed with surgical resection to achieve complete removal and potential long-term survival. This approach is guided by the **"curative resection"** principle in oncology, where complete tumor removal is feasible when anatomical and functional criteria are met.

**Why the Correct Answer is Right**
Surgical resection (hepatectomy) is the treatment of choice for solitary, resectable liver metastases from colorectal cancer. Complete resection with negative margins (R0 resection) significantly improves 5-year survival (up to 40–50%). The liver's dual blood supply and the potential for tumor dormancy in metastatic disease support aggressive surgical intervention when the primary tumor is controlled and the metastasis is isolated.

**Why Each Wrong Option is Incorrect**
**Option A:** Chemotherapy alone is palliative and cannot achieve curative intent in resectable cases.
**Option B:** Radiofrequency ablation is reserved for patients who are poor surgical candidates, not the first-line treatment.
**Option D:** Observation is inappropriate for a solitary metastasis with curative potential.

**Clinical Pearl**
Never forget: **"Resectable liver metastases from colorectal cancer are surgical candidates first, chemotherapy adjuncts later."** The key is to assess tumor resectability (size, location, vascular involvement) and ensure no extrahepatic disease.

**Correct Answer: C. Surgical resection**

✓ Correct Answer: A. Surgery