Assertion (A): Carbon monoxide, when inhaled for a long duration, causes death.
Reason (R): Carbon monoxide combines with haemoglobin.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both Assertion (A) and Reason (R) are correct, and R is the correct explanation of A.
In an Assertion-Reason question, each statement is checked for truth first, and then R is tested as the cause of what A describes.
Assertion — correct. Breathing carbon monoxide for a long time is poisonous and can be fatal.
Reason — correct. Carbon monoxide combines with the haemoglobin of the blood to form carboxyhaemoglobin, and it binds far more firmly than oxygen does.
Haemoglobin taken up by carbon monoxide can no longer carry oxygen to the body, so the body’s cells are starved of oxygen; this is why the gas kills, so R explains A.