**Core Concept**
Ethambutol is a bacteriostatic agent used in the treatment of tuberculosis (TB), primarily targeting the growth and multiplication of Mycobacterium tuberculosis. Its mechanism of action involves inhibiting the synthesis of the bacterial cell wall, specifically by interfering with the arabinosyl transferase enzyme.

**Why the Correct Answer is Right**
Ethambutol works by competitively inhibiting the arabinosyl transferase enzyme, which is essential for the synthesis of arabinogalactan and lipoarabinomannan, critical components of the Mycobacterium tuberculosis cell wall. This inhibition prevents the bacterial cell wall from forming properly, ultimately leading to the bacteriostatic effect. Ethambutol is often used in combination with other antitubercular agents to enhance its efficacy and reduce the risk of resistance.

**Why Each Wrong Option is Incorrect**
**Option A:** Isoniazid (INH) is a bactericidal agent, meaning it directly kills Mycobacterium tuberculosis cells, rather than inhibiting their growth.
**Option B:** Rifampicin is also a bactericidal agent that targets the RNA polymerase enzyme, preventing the transcription of essential bacterial genes.
**Option D:** Pyrazinamide is bactericidal against semi-dormant tubercle bacilli in acidic environments, such as within macrophages.

**Clinical Pearl / High-Yield Fact**
It's essential to monitor patients on ethambutol therapy for visual disturbances, as the drug can cause optic neuritis, leading to decreased visual acuity and even permanent vision loss. Regular ophthalmological check-ups are necessary to detect any potential side effects early on.

**✓ Correct Answer: C. Ethambutol**