If the contacts of a motor starter or controller fail to drop out when the 'stop' button is depressed, what could be the cause?

Correct Answer: Option B — stop contacts have become welded together

Welded contacts occur when high inrush or fault currents cause localized melting at the contact interface. If the contacts fuse together, the motor will continue to run even when the stop button is pressed because the circuit remains closed. This is a critical failure requiring immediate inspection and contact replacement.