When a fuel oil tank is being topped off during bunkering operations, the tank valve should be closed __________.

Correct Answer: Option B — after the shore pumps are stopped

Closing tank valves after shore pumps are stopped prevents the development of excessive backpressure in the filling lines. If valves are closed while pumps are active, the resulting pressure spike can cause hose failure or pipe rupture, leading to a significant pollution incident in violation of MARPOL and 33 CFR.