Explanation:
A centrifugal pump is a type of pump that uses centrifugal force to create pressure and move fluids. It consists of an impeller that rotates and creates a vacuum at the center, which draws in the fluid. The fluid then moves radially outward due to centrifugal force and is discharged at a higher pressure.

Manometer Head:
The manometer head is the pressure head measured by a manometer, which is a device used to measure the pressure of a fluid. In the context of a centrifugal pump, the manometer head represents the pressure head at the outlet of the pump.

Total Head:
The total head is the sum of the pressure head, velocity head, and elevation head. In the context of a centrifugal pump, the total head represents the total energy imparted to the fluid by the pump.

Head Developed:
The head developed by a centrifugal pump is the difference between the total head at the outlet and the total head at the inlet. It represents the increase in energy imparted to the fluid by the pump.

Explanation of the Options:
a) If the manometer head is greater than the total head, it means that the pressure at the outlet is higher than the pressure at the inlet. In this case, the pump will not start delivering the liquid because there is no pressure difference to drive the flow.

b) When the head developed tends to exceed the manometric head, it means that the pump is imparting enough energy to the fluid to overcome the pressure at the outlet. This creates a pressure difference that drives the flow, and the pump starts delivering the liquid.

c) If the head developed in a centrifugal pump is due to the pressure head only, it means that there is no increase in energy imparted to the fluid. In this case, the pump will not start delivering the liquid because there is no pressure difference to drive the flow.

d) If the head developed is negligible, it means that the increase in energy imparted to the fluid by the pump is very small. In this case, the pump will not start delivering the liquid because there is not enough energy to overcome the pressure at the outlet.

Conclusion:
The correct answer is option B, which states that the centrifugal pump will start delivering the liquid when the head developed tends to exceed the manometric head. This means that the pump is imparting enough energy to the fluid to create a pressure difference and drive the flow.