It is dangerous to leave the car engine running in a closed garage, because it may cause serious pollution due to poisoning by emission of

Answer: Option B

The extremely high concentrations of carbon monoxide produced by an engine can raise CO concentrations in a closed building so quickly that a person may collapse before they even realize there is a problem.
Carbon monoxide reduces the amount of oxygen to the brain, causing CO intoxication, and lack of reasoning. Hence option D is correct answer.