**Core Concept**
The question is testing the understanding of the most suitable method for detecting latent tuberculosis infection (LTBI) in a community. The correct answer relies on the principle of detecting the immune response to Mycobacterium tuberculosis in individuals who are infected but not necessarily symptomatic.

**Why the Correct Answer is Right**
The Mantoux test, also known as the tuberculin skin test (TST), is the most widely used method for detecting LTBI. It involves injecting a small amount of purified protein derivative (PPD) of M. tuberculosis into the skin, and the resulting induration (not just redness) is measured 48-72 hours later. A positive test indicates that the individual has been exposed to M. tuberculosis and has mounted an immune response. The TST is a simple, low-cost, and widely available test that is useful for screening large populations.

**Why Each Wrong Option is Incorrect**
* **Option A:** Interferon-gamma release assays (IGRAs) are more specific than the TST but are not the most appropriate choice for assessing the prevalence of tuberculosis infection in a community due to their higher cost and limited availability.
* **Option B:** Chest X-rays are useful for diagnosing active tuberculosis but are not suitable for detecting latent infection.
* **Option C:** Sputum microscopy is primarily used for diagnosing active pulmonary tuberculosis and is not suitable for detecting latent infection.

**Clinical Pearl / High-Yield Fact**
The TST is not suitable for individuals who have received the BCG vaccine, as it can lead to false-positive results. In such cases, IGRAs are a better choice for detecting LTBI.

**Correct Answer:** C. Chest X-rays are useful for diagnosing active tuberculosis but are not suitable for detecting latent infection.