Which of the following conditions would be hazardous if you were using two centrifugal pumps to discharge a flammable liquid?

Correct Answer: Option C — Each pump operating at a different speed and discharging into a common line.

Discharging into a common line with centrifugal pumps operating at different speeds is hazardous because the higher-speed pump develops greater head, deadheading the slower pump. This lack of flow through the slower pump leads to rapid heat buildup and potential ignition of flammable cargo.