**Core Concept**
The question is testing the safety profile of antitubercular drugs in patients with liver dysfunction, specifically hepatitis. **Isoniazid** is a first-line antitubercular medication that can cause hepatotoxicity, whereas other options are safer alternatives in such patients.

**Why the Correct Answer is Right**
Pyrazinamide is generally considered safe in patients with hepatitis. It is a key component of the directly observed treatment, short-course (DOTS) regimen for tuberculosis and is less likely to cause hepatotoxicity compared to isoniazid. The mechanism of action of pyrazinamide involves the inhibition of fatty acid synthase I, which is essential for the growth of Mycobacterium tuberculosis. In contrast, isoniazid is metabolized in the liver and can cause liver damage, especially in patients with pre-existing liver disease.

**Why Each Wrong Option is Incorrect**
**Option A:** Isoniazid is not safe in patients with hepatitis due to its potential to cause hepatotoxicity.
**Option B:** Ethambutol can cause optic neuritis, which is unrelated to liver function, making it an incorrect choice in the context of this question.
**Option C:** Rifampicin is also a first-line antitubercular medication but can cause liver damage, especially when used in combination with other hepatotoxic agents.

**Clinical Pearl / High-Yield Fact**
In patients with liver dysfunction, it is essential to choose antitubercular medications that are less likely to cause hepatotoxicity. Pyrazinamide is a safer alternative to isoniazid in such cases.

**Correct Answer:** D. Pyrazinamide