A mixture of methane, carbon dioxide, hydrogen and hydrogen sulphide is called..................

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Components**: The question mentions a mixture of four gases: methane (CH₄), carbon dioxide (CO₂), hydrogen (H₂), and hydrogen sulfide (H₂S).

2. **Identifying the Mixture**: These gases are commonly found together in certain biological processes, particularly in anaerobic digestion.

3. **Biogas Production**: The primary context for these gases is biogas, which is produced through the breakdown of organic matter by microorganisms in the absence of oxygen.

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