ANS:D - None of these

The factor that does not contribute to the pressure drop in a pipeline among the options provided is: None of these. Here’s an explanation of each factor:

1. Velocity of fluid: The velocity of the fluid is a significant factor contributing to the pressure drop in a pipeline. Higher velocities lead to increased frictional losses and hence higher pressure drops.
2. Size of pipe: The size of the pipe affects the pressure drop through its influence on the flow velocity. Smaller pipes generally result in higher velocity and consequently higher pressure drop due to increased frictional losses.
3. Length of pipe and number of bends: Longer pipes and a greater number of bends contribute to higher pressure drop. This is because they increase the total frictional resistance encountered by the fluid as it flows through the pipeline.