Fill in the blanks by suitable words to make correct statements:
When burnt, _________ release toxic gases into the air causing air pollution.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks us to fill in the blank with a suitable word that describes a material that releases toxic gases when burnt.

2. **Identifying the Material**: We need to think about materials that are commonly burnt and known to release harmful gases.

3. **Considering Common Materials**: Among the materials we use, plastics are widely known for releasing toxic gases when burnt.

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