**Core Concept**
Lepromatous leprosy is a type of leprosy characterized by a strong bacterial load and a poor immune response. The treatment of lepromatous leprosy involves a combination of antibiotics to reduce the bacterial load and prevent the progression of the disease.

**Why the Correct Answer is Right**
In lepromatous leprosy, dapsone is continued for 1 year as a part of the multidrug therapy (MDT) regimen. This prolonged treatment duration is necessary to ensure that the bacterial load is adequately reduced and the disease is brought under control. The World Health Organization (WHO) recommends the use of MDT, which includes a combination of rifampicin, clofazimine, and dapsone, for the treatment of lepromatous leprosy. The continuation phase of dapsone is essential to prevent the recurrence of the disease and to reduce the risk of drug resistance.

**Why Each Wrong Option is Incorrect**
**Option A:** 9 days is an inadequate duration for the continuation phase of dapsone in lepromatous leprosy. A shorter treatment duration may not be sufficient to achieve the desired outcome and may increase the risk of drug resistance.

**Option B:** 90 days is also an inadequate duration for the continuation phase of dapsone in lepromatous leprosy. While it is longer than 9 days, it is still not sufficient to ensure that the bacterial load is adequately reduced.

**Option D:** 10 years is an excessively long duration for the continuation phase of dapsone in lepromatous leprosy. While prolonged treatment may be necessary in some cases, 10 years is not a standard recommendation for the treatment of lepromatous leprosy.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the treatment of lepromatous leprosy requires a multidisciplinary approach, including the use of antibiotics, surgery, and social support. The treatment should be tailored to the individual patient's needs and should be continued for a sufficient duration to ensure that the disease is brought under control.

✓ Correct Answer: C. 1 years