Chlorophyll contains

$CO$ (Carbon monoxide) is a neutral oxide of carbon,but it acts as a very strong field ligand and associates with metals to form complex compounds. These complex compounds are very useful in metallurgical processes. $CO$ is a poisonous gas because:

In hemoglobin, the metal ion present is:

The metals present in insulin and haemoglobin are respectively:

Which statement is true for sodium nitroprusside?

Which chelating ligand is used to remove excess $Cu$ poisoning in plants and animals?