The output of the XOR gate is HIGH when ____ input(s) is/are HIGH.

The output of an XOR gate is HIGH when there is an odd number of HIGH inputs. The XOR (exclusive OR) function operates under the principle that it outputs TRUE (or HIGH) only when the number of true inputs is odd.

In the case of a two-input XOR gate, it will produce a HIGH output when exactly one of the inputs is HIGH, meaning it satisfies the requirement of having an odd number of HIGH inputs (which in this scenario is one). If both inputs are HIGH, the output will be LOW, and if both are LOW, the output is also LOW.

Thus, the correct answer – indicating that the output is HIGH when one input is HIGH – accurately reflects how an XOR gate functions in digital logic.