Molten soap mass is transported by a __________ pump.

Answer: Option C

Molten soap mass is a highly viscous fluid.

Gear pumps are positive displacement pumps that are highly effective for handling viscous fluids such as oils, syrups, and molten soap.

They operate by trapping the fluid in the cavities between the gear teeth and the pump casing, and transporting it from the inlet to the outlet side.

Diaphragm pumps are better suited for corrosive or slurry-type fluids, not necessarily viscous molten materials.

Reciprocating pumps are also positive displacement but are generally used for low flow, high-pressure applications and are less efficient with viscous fluids.

Centrifugal pumps are not suitable for high-viscosity fluids as their performance drops significantly.

Therefore, for molten soap mass, a gear pump is the most appropriate choice due to its ability to handle viscous materials efficiently.