Teacher advised his students, "Never sleep in a closed room with burning or smouldering coal fire in it" because ________.
1 Incomplete combustion of coal gives carbon monoxide gas.
2 Complete combustion of coal gives sulphur dioxide gas.
3 Rapid combustion of coal leads to fire accidents.
4 Coal has high calorific value and gives a large amount of heat.

Correct option is A

Correct Answer: (a)
Explanation
When coal burns in a closed room, there is insufficient oxygen available. Due to this, incomplete combustion takes place, producing carbon monoxide (CO} instead of carbon dioxide (CO₂}.
Carbon monoxide is:
· Colourless
· Odourless
· Highly poisonous
It combines with haemoglobin about 200–250 times more strongly than oxygen, reducing the blood's oxygen-carrying capacity. This can cause suffocation, unconsciousness, and even death.
Therefore, one should never sleep in a closed room with burning or smouldering coal.
Hence, the correct answer is Option (a}.
Additional Information
• Complete combustion: Carbon + Oxygen → Carbon dioxide (CO₂}
• Incomplete combustion: Carbon + Limited oxygen → Carbon monoxide (CO}
• Carbon monoxide poisoning symptoms include:
· Headache
· Dizziness
· Nausea
· Confusion
· Unconsciousness
• CO is called the "silent killer" because it has no colour or smell.