Which of the following is not correct about carbon monoxide? 

The carboxyhaemoglobin (haemoglobin bound to CO) is less stable than oxyhaemoglobin. This statement is wrong because, actually, carboxyhaemoglobin (here, hemoglobin bound to CO) is about 300 times more
stable than the oxygen-haemoglobin complex.
(1) CO forms carboxyhaemoglobin.
(2) CO reduces oxygen carrying ability of blood.
(4) CO is produced due to incomplete combustion of coke, hydrocarbons, etc.
$2C+O_2\stackrel{\Delta }{⟶}\underset{\left(g\right)}{2CO}$
All (1),(2), and (4) statements are true.