Final answer:
Pass medium solids pumps are characterized by no metal-to-metal contact, self-priming, non-pulsating discharge, and minimal flow back/leakage when stopped.
Step-by-step explanation:
To determine the characteristics associated with passing medium solids pumps, we need to review the given options. No metal-to-metal contact is a characteristic associated with these pumps as they are designed to prevent metal components from contacting each other.
Self-priming is another characteristic of pass medium solids pumps, enabling them to automatically remove air from the suction line and start pumping liquids. A long-term dry run is not a characteristic of these types of pumps as they require a liquid medium for operation. Non-pulsating discharge is another characteristic, ensuring that the flow rate is steady and continuous. Finally, when stopped, very little flow back/leakage is associated with these pumps as they are designed to minimize backflow and leakage when not in operation.