The correct answer is: A. Restricted
When the signal is blank in MACLS system, it is treated as showing restricted aspect. This means that the signal is not available and cannot be used. The signal may be blank due to a number of reasons, such as a loss of signal, a problem with the equipment, or a deliberate attempt to block the signal.
The other options are incorrect because they do not accurately describe the situation when the signal is blank in MACLS system. Option B, “Most restricted,” is incorrect because it implies that the signal is more restricted than it actually is. Option C, “Defective,” is incorrect because it implies that the signal is broken or damaged, which is not necessarily the case. Option D, “None of these,” is incorrect because it does not accurately describe the situation when the signal is blank in MACLS system.