**Core Concept**
Cutaneous tuberculosis (TB) is a form of extrapulmonary TB that affects the skin, often resulting from the reactivation of latent TB infection or exogenous infection through direct inoculation of the bacteria. The skin manifestations of TB can vary widely in presentation and severity.

**Why the Correct Answer is Right**
The most common type of cutaneous TB is tuberculid, a hypersensitivity reaction to the tubercle bacillus. Tuberculids typically present as erythematous, papular, or plaquelike lesions that may be localized or generalized, often accompanied by systemic symptoms such as fever and malaise. The pathogenesis of tuberculids involves the activation of T-cell immunity against the tubercle bacillus, leading to the release of cytokines and the recruitment of inflammatory cells to the affected skin.

**Why Each Wrong Option is Incorrect**
**Option A:** Lichen scrofulosorum is a rare form of cutaneous TB that typically affects children and adolescents, presenting as small, follicular papules on the trunk. While it is a type of cutaneous TB, it is less common than tuberculid.
**Option B:** Lupus vulgaris is a form of cutaneous TB that presents as a chronic, progressive disease with characteristic lesions on the face, neck, and arms. While it is a well-known form of cutaneous TB, it is less common than tuberculid.
**Option C:** Erythema induratum is a form of cutaneous TB that typically affects the calves of young women, presenting as recurrent, tender nodules. While it is a type of cutaneous TB, it is less common than tuberculid.

**Clinical Pearl / High-Yield Fact**
Tuberculids should be considered in the differential diagnosis of any patient presenting with skin lesions, especially in regions with high TB prevalence or in patients with a history of TB exposure.

**Correct Answer:** C. Tuberculid. Tuberculid.