**Core Concept**
The World Health Organization (WHO) recommends different durations of treatment for leprosy based on the bacillary load and the patient's response to treatment. Multibacillary leprosy is a more severe form of the disease, characterized by a high bacterial load and multiple skin lesions.

**Why the Correct Answer is Right**
Multibacillary leprosy requires a longer duration of treatment to ensure that all the bacteria are eliminated and to prevent the development of drug resistance. The WHO recommends a treatment duration of 12 months (1 year) for multibacillary leprosy, consisting of rifampicin, clofazimine, and dapsone. This prolonged treatment period helps to minimize the risk of relapse and ensure that the patient is cured of the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** 6 months is the recommended treatment duration for paucibacillary leprosy, a less severe form of the disease characterized by a low bacterial load and fewer skin lesions. This duration is not sufficient for multibacillary leprosy.

**Option C:** 2 years is not the recommended treatment duration for multibacillary leprosy. While longer treatment durations may be necessary in some cases, 2 years is not the standard recommendation.

**Option D:** 5 years is excessively long and not recommended by the WHO for the treatment of multibacillary leprosy. This duration would be more suitable for chronic conditions requiring long-term management.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the treatment duration for leprosy may vary depending on the country and region, and it's crucial to follow the guidelines recommended by the local health authorities. Additionally, patients with multibacillary leprosy may require regular follow-up and monitoring to ensure that they complete the full course of treatment and do not develop any complications.

**✓ Correct Answer: B. 1 year**