**Explanation:**

**Centrifugal Pump:**
A centrifugal pump is a type of dynamic pump that uses a rotating impeller to increase the pressure and flow of a fluid. It is widely used in various industries for pumping liquids such as water, oil, and chemicals.

**Impeller Blades:**
The impeller is the rotating component of the centrifugal pump that transfers energy to the fluid. It consists of curved blades that are designed to increase the velocity of the fluid as it passes through the pump.

**Efficiency of a Centrifugal Pump:**
The efficiency of a centrifugal pump is a measure of how effectively it converts the input power into useful work. It is expressed as a percentage and is calculated by dividing the output power by the input power and multiplying by 100.

**Effect of Impeller Blade Shape on Efficiency:**
The shape of the impeller blades plays a significant role in determining the efficiency of a centrifugal pump. Different impeller blade shapes can result in different flow patterns and hydraulic losses, which ultimately affect the overall efficiency of the pump.

**Explanation of Option 'B': Bent, backward:**
Option 'B' states that the impeller blades should be bent backward to achieve maximum efficiency. This means that the blades should be curved in the opposite direction of the rotation of the impeller.

**Reasoning behind Option 'B':**
When the impeller blades are bent backward, it creates a higher pressure on the backside of the blade and a lower pressure on the front side. This pressure difference helps to push the fluid in the desired direction and increases the efficiency of the pump. Additionally, the backward bend of the blades helps to reduce the hydraulic losses and recirculation within the pump, further enhancing its efficiency.

**Advantages of Bent, Backward Impeller Blades:**
1. Increased Pressure Difference: The backward bend of the blades creates a higher pressure on the backside, which helps to push the fluid forward more effectively.
2. Reduced Hydraulic Losses: The backward bend helps to minimize the hydraulic losses and recirculation within the pump, resulting in improved efficiency.
3. Better Flow Control: The backward bend of the blades allows for better flow control and reduces the risk of cavitation.

Overall, the bent, backward impeller blades provide better performance and efficiency in a centrifugal pump compared to other blade shapes.