**Core Concept**
Acute Necrotizing Ulcerative Gingivitis (ANUG) is a severe form of periodontal disease characterized by the rapid onset of necrotic ulcerative lesions on the interdental papillae and marginal gingiva. This condition is often associated with poor oral hygiene, stress, and smoking.

**Why the Correct Answer is Right**
ANUG is best visualized using a **periodontal probe**, which allows for the assessment of the extent of tissue destruction and the presence of necrotic debris. The interdental papillae are typically affected, and the use of a periodontal probe enables the clinician to evaluate the depth of the ulcerative lesions and the presence of bleeding on probing. This is crucial for diagnosing ANUG and distinguishing it from other periodontal conditions.

**Why Each Wrong Option is Incorrect**
**Option A:** Radiographs are not the best tool for visualizing ANUG, as they may not show the extent of tissue destruction or the presence of necrotic debris.
**Option B:** A microscope may be used to examine the histopathological changes associated with ANUG, but it is not the best tool for visualizing the condition in its clinical presentation.
**Option C:** A mirror is a basic tool for examining the oral cavity, but it is not sufficient for visualizing the extent of tissue destruction and necrotic debris associated with ANUG.

**Clinical Pearl / High-Yield Fact**
ANUG is often associated with poor oral hygiene, stress, and smoking, and its diagnosis is often delayed due to the lack of awareness among dental professionals. Early recognition and treatment of ANUG are crucial to prevent the progression of the disease and its potential complications.

**Correct Answer: C. Mirror examination**