Assertion: Carbon monoxide when inhaled for longer duration causes death.
Reasoning: Carbon monoxide combines with haemoglobin.
Answer & explanation
Correct answer: option 1
The Assertion is correct because Carbon monoxide when inhaled it combines with hemoglobin of the blood to form Carboxyhemoglobin which inhibits the transport of oxygen in the body.
Carbon monoxide has a much stronger binding to hemoglobin than Oxygen, so the given Reason is the correct explanation to the Assertion.
Hence, the correct answer is "Option 1".