**Core Concept**
The Child-Pugh score is a clinical scoring system used to assess the prognosis of patients with cirrhosis, a condition characterized by liver scarring due to chronic liver disease. It takes into account several factors, including serum bilirubin and albumin levels, prothrombin time, and the presence of ascites and encephalopathy.

**Why the Correct Answer is Right**
The Child-Pugh score is used to predict the severity of liver disease and to guide treatment decisions. It is based on the accumulation of bilirubin and the reduction of albumin and clotting factors, which are indicative of liver dysfunction. The presence of ascites and encephalopathy are also important indicators of liver disease severity. The score is calculated by assigning points for each of these factors, with higher scores indicating more severe liver disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Child-Pugh score is not used to assess liver function in patients with acute liver failure.
**Option B:** This option is incorrect because the Model for End-Stage Liver Disease (MELD) score is a different scoring system used to assess liver disease severity, particularly in patients with cirrhosis who are candidates for liver transplantation.
**Option C:** This option is incorrect because the Child-Pugh score is not used to assess the effectiveness of liver transplantation.

**Clinical Pearl / High-Yield Fact**
The Child-Pugh score is a useful tool for predicting the prognosis of patients with cirrhosis and guiding treatment decisions, but it should be used in conjunction with other clinical assessments and liver function tests.

**Correct Answer:** C. Child-Pugh score is used to assess the prognosis of patients with cirrhosis.