In sickle cell anaemia, the sequence of amino acid from first to seventh position of `beta`-chain of haemoglobin S (HbS) is
A. His, Leu, Thr, Pro, Glu, Val, Val
B. Val, His, Leu, Thr,Pro,Glu, Glu
C. Thr, His Pro, Val, Pro, Val, Glu
D. Glu, His, Leu, Pro, Val, Glu, Glu