**Core Concept**
The question is testing the management of neonates exposed to a mother with sputum-positive tuberculosis (TB), specifically the use of chemoprophylaxis to prevent the development of TB in the neonate. The underlying principle is the use of antitubercular therapy to prevent the transmission of TB from an infected mother to her infant.

**Why the Correct Answer is Right**
The World Health Organization (WHO) recommends chemoprophylaxis for neonates exposed to a mother with sputum-positive TB. The recommended regimen is a combination of isoniazid (INH) and pyrazinamide for 6 months, starting within the first few weeks of life. This is based on the understanding that the neonate is at high risk of developing TB due to the close proximity to the infected mother and the potential for airborne transmission. The use of INH and pyrazinamide targets the latent TB infection in the neonate, preventing the progression to active disease.

**Why Each Wrong Option is Incorrect**
* **Option A:** Isoniazid monotherapy is not recommended for chemoprophylaxis in neonates exposed to sputum-positive TB. While INH is an essential component of the regimen, it is typically used in combination with other antitubercular drugs to ensure effective treatment.
* **Option B:** Rifampicin is an essential component of TB treatment, but it is not recommended as monotherapy for chemoprophylaxis in neonates. Rifampicin can also be hepatotoxic, making it a less desirable option for chemoprophylaxis in this population.
* **Option C:** The recommended duration of chemoprophylaxis is 6 months, not 3 months. The longer duration is necessary to ensure that the latent infection is fully treated and to prevent the development of TB in the neonate.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the risk of TB transmission from mother to infant is higher if the mother has sputum-positive TB. In such cases, chemoprophylaxis should be initiated promptly, and the neonate should be closely monitored for signs of TB infection.

**Correct Answer: C. Isoniazid and pyrazinamide for 6 months.**