What type of work does District 12 cover?

District 12 is primarily known for its coal mining operations, which inherently involve outdoor work. The nature of this industry requires workers to engage in tasks that are performed outside, such as extracting coal from the ground, thus making outdoor labor the dominant type in this district. The focus on mining reflects the economic activities prevalent in District 12, and while some associated tasks may occur indoors, such as administrative work or maintenance, the core work characteristic of the district is outdoor mining.

The other options do not accurately represent the essence of District 12's primary focus on mining activities. Indoor work is not a defining feature of this district, nor is it exclusively limited to outdoor work without any indoor elements. Additionally, training, while important, is not the primary type of work associated with District 12. The main activities revolve around the labor-intensive processes of coal mining in an outdoor setting.