**Core Concept**
Leprosy elimination is a global health goal aimed at reducing the incidence and prevalence of leprosy to a level where it no longer constitutes a public health problem. The World Health Organization (WHO) has established specific criteria for leprosy elimination, focusing on a significant reduction in new cases and a low prevalence rate.

**Why the Correct Answer is Right**
Leprosy elimination is defined as a prevalence of less than 1 case per 10,000 population. This threshold is based on the idea that a prevalence rate of 1 case per 10,000 population indicates a low risk of transmission and a manageable burden of disease for healthcare systems. The WHO has set this target to guide national leprosy control programs and ensure that leprosy remains a rare disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the WHO's criteria for leprosy elimination. The correct threshold is not a specific percentage or ratio, but rather a prevalence rate of less than 1 case per 10,000 population.

**Option B:** This option is incorrect because it is an arbitrary threshold that has not been established by the WHO or other global health authorities. Leprosy elimination is a specific goal with well-defined criteria, and this option does not align with those criteria.

**Option C:** This option is incorrect because it implies a specific time frame for leprosy elimination, which is not a requirement for achieving this goal. Leprosy elimination is a long-term goal that requires sustained efforts and commitment from national health authorities.

**Option D:** This option is incorrect because it is not a feasible or realistic target for leprosy elimination. The goal is to reduce the prevalence rate to a level where leprosy no longer constitutes a public health problem, not to eliminate the disease entirely.

**Clinical Pearl / High-Yield Fact**
The WHO's criteria for leprosy elimination serve as a benchmark for national health authorities to measure progress and assess the effectiveness of their leprosy control programs. This goal is critical for ensuring that leprosy remains a rare disease and that healthcare systems are equipped to manage and treat affected individuals.

**Correct Answer: C.**