'बायोगैस' में मुख्य रूप से कौन सी गैस होती है?

उत्तर: (C) मीथेन / Methane — Biogas contains mainly methane (CH₄, 50-75%) along with CO₂, H₂S, and traces of other gases. It is produced by anaerobic decomposition of organic matter (cattle dung, agricultural waste). It is a rene...