The correct option is (a).
Explanation
Substances are classified based on their ability to burn in the presence of air. Materials that undergo combustion to produce heat and light are termed combustible substances, while those that do not burn are called non-combustible substances.Statement-wise Analysis:
- Statement 1 is Correct: Wood and paper are carbon-based organic materials. They readily catch fire and burn in the presence of oxygen, classifying them as combustible substances.
- Statement 2 is Incorrect: Glass is a non-crystalline, inorganic solid that does not catch fire or sustain burning. It is a non-combustible substance.
- Statement 3 is Incorrect: Stone is a non-combustible material. Similarly, iron nails (bulk iron) do not burn in a standard flame, although fine iron filings may burn. In the general classification of substances, both stone and iron nails are considered non-combustible.
Key Takeaway: Combustibility is a chemical property where a substance reacts with oxygen to release energy. Common combustible materials include wood, paper, and charcoal, whereas glass, stone, and bulk metals are non-combustible.