Final answer:
An Exclusive-OR gate outputs HIGH if exactly one of its inputs is HIGH, acting as a controlled inverter.
Step-by-step explanation:
The characteristic of an Exclusive-OR gate, often symbolized as XOR, is that it outputs a HIGH (or true) signal if the number of HIGH inputs is odd. Specifically, an XOR gate outputs a HIGH signal if one, and only one, of its two inputs is HIGH. This can be seen as the gate performing a logical 'either/or' operation, hence the name 'Exclusive-OR'. If both inputs are LOW or both are HIGH, the XOR gate outputs a LOW (or false) signal. This behavior distinguishes it from other logic gates, such as the AND gate, which outputs HIGH only when all inputs are HIGH, or an OR gate, which outputs HIGH when any input is HIGH. Therefore, the correct characteristic of an Exclusive-OR gate as described is that it acts as a controlled inverter, reflecting option A).