Explanation: In a LORAN (Long Range Navigation) system, blinking is a crucial error indicator. LORAN relies on precise timing differences between pulsed radio signals from a master and multiple secondary stations. If one of these stations experiences an internal fault, loses synchronization, or transmits an unreliable signal, it will intentionally alter its signal pattern to "blink." This **blinking** serves as an immediate warning to the receiving operator (A) that there is a problem with the transmitting station or its signal. Continuing to use the faulty signal for navigation could lead to significant position errors. Operators are trained to disregard blinking signals when plotting their position. Option B is incorrect because LORAN is always "in use" when operational; blinking indicates an abnormal condition, not normal operation. Option C is incorrect; while LORAN systems require calibration and accurate alignment, blinking is an indication of a problem at the *transmitter*, not a general need for user alignment or recalibration. Therefore, D is also incorrect.