**Core Concept**
The earliest sign of tuberculosis of the vocal cords is related to the inflammatory response and the body's attempt to fight off the infection. Tuberculosis of the larynx, particularly the vocal cords, often presents with subtle changes in the mucosa, which can be challenging to diagnose.

**Why the Correct Answer is Right**
The correct answer is **B. Hyperemia of the free margin**. Hyperemia refers to increased blood flow to the affected area, resulting in redness and swelling. In the case of tuberculosis of the vocal cords, hyperemia of the free margin is the earliest sign, indicating the body's initial response to the infection. This occurs due to the release of inflammatory mediators, such as histamine and bradykinin, which cause increased blood flow to the affected area. The free margin of the vocal cord is the edge of the mucosal fold where the vocal cord meets the arytenoid cartilage.

**Why Each Wrong Option is Incorrect**
**Option A:** Mouse nibbled appearance is a more advanced sign of vocal cord tuberculosis, characterized by a rough, irregular surface resembling mouse nibbles. It is not the earliest sign.
**Option C:** Turban epiglottitis is a complication of tuberculosis, where the epiglottis becomes inflamed and swollen, resembling a turban. This is not the earliest sign of vocal cord tuberculosis.
**Option D:** Ulceration of the vocal cord is a later stage of tuberculosis, where the infection causes the formation of ulcers on the surface of the vocal cord. This is not the earliest sign.

**Clinical Pearl / High-Yield Fact**
In cases of suspected vocal cord tuberculosis, a biopsy of the affected area may be required for definitive diagnosis. The biopsy should be performed carefully to avoid causing further damage to the vocal cord.

✓ Correct Answer: B. Hyperemia of the free margin