Correct Answer: Haemoglobin

Solution : The correct option is Haemoglobin

The red colour of human blood is caused by a molecule known as haemoglobin . The protein haemoglobin is present in red blood cells and delivers oxygen from the lungs to the rest of the body's tissues and organs. Haemoglobin also aids in the transfer of carbon dioxide, a byproduct of metabolism, back to the lungs for expiration. The red colour of haemoglobin is a result of its iron content. When it binds with oxygen in the lungs, it forms a complex called oxyhaemoglobin, which is bright red.