Carbon (II) oxide is considered dangerous if inhaled mainly because itcan cause injury to the nervous system

Correct Answer: Competes with oxygen in the blood

Explanation:

• Carbon (II) oxide (CO), also called carbon monoxide, is highly poisonous.
• It binds strongly with haemoglobin in red blood cells, forming carboxyhaemoglobin.
• This binding is over 200 times stronger than that of oxygen, so CO effectively competes with oxygen in the blood and prevents oxygen transport to body tissues.
• Lack of oxygen supply leads to tissue damage, particularly in the brain and heart, and can cause death if exposure is prolonged.

Thus, the main reason CO is dangerous is that it competes with oxygen in the blood.