**Core Concept**
The District TB Control Programme is a public health initiative aimed at controlling tuberculosis at the grassroots level. It focuses on identifying and treating new cases of TB, as well as detecting drug-resistant strains of the disease.

**Why the Correct Answer is Right**
The programme is mainly concerned with **detecting cases and treatment (c)**, as early detection and treatment are crucial in preventing the spread of TB. **Finding out new cases (a)** is also a key component, as it allows for the identification of individuals who require treatment and helps to prevent the transmission of the disease to others. The programme's emphasis on detecting new cases is essential in controlling the spread of TB.

**Why Each Wrong Option is Incorrect**
**Option A:** Finding out new cases is indeed a part of the programme, but it is not the main concern. The programme's scope is broader, encompassing case detection and treatment.
**Option D:** All of the above is incorrect because while the programme does involve finding new cases, detecting resistant cases, and treating cases, its primary focus is on case detection and treatment.
**Option C:** ad is incorrect because finding out resistant cases is not the main concern of the programme.

**Clinical Pearl / High-Yield Fact**
The District TB Control Programme uses a combination of passive and active case-finding strategies to identify new cases of TB. Passive case-finding involves relying on patients to report their symptoms, while active case-finding involves screening high-risk populations, such as household contacts of TB patients.

**✓ Correct Answer: B. ac**