A mutation in one of the genes that codes for haemoglobin alters the affinity of haemoglobin for oxygen. As a result of this mutation, the partial pressure of oxygen needed for haemoglobin to be $50\%$ saturated with oxygen is reduced. Which row indicates the effect of the mutation on the affinity of haemoglobin for oxygen and the change in the position of the oxygen dissociation curve for haemoglobin?
- Ahigher affinity; shift to the left
- Bhigher affinity; shift to the right
- Clower affinity; shift to the left
- Dlower affinity; shift to the right