Lower P50 means higher oxygen affinity and leftward curve shift Steps:

• P50 is the partial pressure (PO2) where hemoglobin is 50% saturated with oxygen.
• Lowering P50 indicates hemoglobin saturates at lower PO2, meaning higher affinity for oxygen.
• Higher affinity causes the oxygen dissociation curve to shift left, as hemoglobin binds oxygen more tightly.
• Thus, the mutation increases affinity and shifts the curve left.

Why B is correct:

• Higher affinity corresponds to a left shift per standard oxygen-hemoglobin dissociation curve principles, where decreased P50 reflects tighter O2 binding.

Why the others are wrong:

• A: Higher affinity pairs with left (not right) shift; right shift indicates lower affinity.
• C: Mutation raises (not lowers) affinity, so lower affinity is incorrect.
• D: Lower affinity would raise P50 and shift right, opposite the mutation's effect.

Final answer: B