The correct option is A Carbon monoxide
Carbon monoxide mainly causes adverse effects in humans by combining with haemoglobin to form carboxyhaemoglobin (HbCO) in the blood. This prevents haemoglobin from carrying oxygen to the tissues, effectively reducing the oxygen-carrying capacity of the blood, leading to hypoxia. Carbon monoxide poisoning occurs after enough inhalation of carbon monoxide (CO). Carbon monoxide is a toxic gas, but, being colourless, odourless, tasteless, and initially non-irritating, it is very difficult for people to detect.