When does an XNOR gate output a HIGH signal?

An XNOR gate outputs a HIGH signal when its inputs are the same, which means both inputs are either HIGH or LOW. This behavior reflects the function of an XNOR gate as a logical equality checker; it produces a HIGH output to signal that the inputs match. Therefore, if you input two HIGH signals, the output will be HIGH as both inputs are the same. Similarly, if both inputs are LOW, the output is again HIGH. This characteristic makes the XNOR gate useful in applications requiring equality detection or comparison logic.

In contrast, if the inputs differ — one HIGH and one LOW — the output will be LOW, indicating that the inputs do not match. Thus, the specific condition for the XNOR gate to produce a HIGH output is when all inputs are the same, confirming the correctness of the chosen answer.