Which of the following statements are correct?
(a) Haemoglobin consist of four protein chains called globins
(b) Alfa chain of haemoglobin contain 141 amino acids
(c) HbA2 is a adult haemoglobin which has two delta chains in place of beta chains
(d)Fetal haemoglobin (HbF) which has two gamma chains in place of the beta chains