The given question involves understanding the relationship between power (P) and discharge (Q) in a centrifugal pump, based on different vane exit angles. The focus is on identifying which vane exit angle corresponds to Curve A in the figure.

### Step-by-step Explanation

1. In centrifugal pumps, the vane exit angle affects the flow characteristics and power consumption. The vane exit angle is the angle at which the fluid leaves the impeller vanes.
2. **Vane Exit Angle Effects:**
   • If the vane exit angle is \(\lt 90^\circ\), the power curve typically forms a concave shape. This is due to the reduction in radial velocity and flow separation, which adjusts the power consumption relative to discharge.
   • A vane exit angle of \(90^\circ\) or more would usually result in different power and discharge characteristics, often leading to linear or other deformed curves.
3. **Analyzing Curve A:**
   • Curve A shows a concave downward relationship between power (P) and discharge (Q), characteristic of a vane exit angle of less than \(90^\circ\).
4. Based on these observations, Curve A corresponds to a vane exit angle of less than \(90^\circ\).

### Conclusion

The correct answer is: vane exit angle of less than 90°.