The correct answer is B) sensor failure. If both the high level and low level alarms are activated for the same address on a centralized control console, the most likely cause is a sensor failure. This is because the sensor is responsible for detecting the levels and triggering the alarms. If the sensor is malfunctioning, it could be registering erroneous readings, causing both the high and low level alarms to activate, even though the actual level may be within the normal range. The other options are incorrect because they do not fully explain the situation. A low level alarm alone (option A) would not trigger both alarms, and a failed alarm (option C) would not result in both alarms being activated. An extremely high level (option D) would not typically trigger both the high and low level alarms simultaneously.