The best methodology to teach the theme 'Factory' would be—

Direct experiential learning is the most effective pedagogy for concrete themes like 'Factory'. Organizing a visit to an industrial plant allows students to observe real processes, workers, machinery, and production cycles firsthand, which makes learning vivid and lasting. NCF-2005 emphasizes experiential and contextual learning over abstract description. A story, expert talk, or documentary are secondary aids but cannot replace direct observation. Field visits also promote inquiry, questioning, and integration of multiple subjects. Hence option (3) is the best methodology.