**Core Concept**
The best method to find out cases of TB in a community is to use a combination of active and passive case-finding strategies, focusing on high-risk populations and areas with high incidence rates. This approach involves identifying individuals with symptoms suggestive of TB and screening them for the disease, as well as actively seeking out cases through contact tracing and other methods.

**Why the Correct Answer is Right**
The World Health Organization (WHO) recommends a combination of active and passive case-finding strategies for TB control. Active case-finding involves systematic screening of high-risk populations, such as those with HIV/AIDS, diabetes, or silicosis, as well as individuals living in areas with high TB incidence rates. Passive case-finding, on the other hand, relies on individuals presenting to healthcare facilities with symptoms suggestive of TB. This approach allows for early detection and treatment of TB cases, reducing the risk of transmission to others.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not a recognized method for finding cases of TB in a community.
* **Option B:** While contact tracing is an important tool for TB control, it is not the best method for finding cases in a community.
* **Option D:** This option is not a valid method for finding cases of TB.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the most effective TB control programs use a combination of active and passive case-finding strategies, focusing on high-risk populations and areas with high incidence rates.

**Correct Answer: C. Contact tracing and systematic screening.**