Explanation:

All the statements are correct. It was discovered in the 1960s that CO can be endogenously produced in the body by heme oxygenase (HO) metabolism of heme to produce CO.
Carbon monoxide is produced naturally by the human body as a signaling molecule. Thus, carbon monoxide may have a physiological role in the body, such as a neurotransmitter or a blood vessel relaxant.
When carbon monoxide binds to hemoglobin, it increases the affinity of hemoglobin for oxygen and shifts the oxygen dissociation curve to the left. The resulting decrease in sickling tendency could have clinical benefit, and carbon monoxide has been suggested as a treatment for sickle-cell disease. Furthermore, in sickle-cell disease, as in other hemolytic diseases, endogenous carbon monoxide production is increased because of increased heme catabolism.
(Reff.
https://www.ncbi.nlm.nih.gov/pubmed/11780692
)

Sickle Cell Anaemia affects the shape of red blood cells, changing them from a flattened disc to a sickle or crescent shape. Whereas normal red blood cells are smooth and move easily through blood vessels, sickle blood cells are hard, inflexible and tend to clump together, causing them to get stuck in blood vessels as blood clots, thereby blocking the flow of blood. This can cause pain, blood vessel damage and a low red blood cell count (anaemia) due to the more fragile nature of sickle blood cells. The abnormal sickle shape is due to the presence of abnormal haemoglobin (haemoglobin S), which contains abnormal beta polypeptide with a single amino acid substitution at position 6 along the polypeptide chain (the alpha chain is normal). The abnormal b chain reduces the amount of oxygen inside the red blood cell, altering its shape.
(Reff- https://www.ebi.ac.uk/interpro/potm/2005_10/Page2.htm )