Ключевые слова: activity, background, building, cave, concrete, construction, danger, dark, dirt, dirty, discover, discovery, engineering, entrance, equipment, excavation, exploration, explorer, geology, hard, heavy, helmet, industrial, industry, iron, job, light, machine, man, material, metal, miner, passage, people, person, rail, railroad, rails, railway, road, rock, safety, site, structure, technology, transport, transportation, tube, tunnel, tunneling, underground, vehicle, work, worker,