How many total signals must be high for a high output in a 4 input AND gate?

In a 4-input AND gate, the output is high only when all of its inputs are high. This is the fundamental characteristic of an AND gate, which operates on the principle of logical conjunction. Each input contributes to the overall output condition, and only when every single input is at a high signal level does the output become high.

In this case, since there are four inputs, the correct answer indicates that all four signals must be high for the output to be high. If any one of the inputs is low, the output will be low regardless of the states of the other inputs. This property of the AND gate is crucial in digital logic design, as it ensures that the gate can act as a reliable control mechanism for activating outputs based on multiple conditions.

This highlights the importance of understanding the behavior of logic gates, particularly in applications such as circuit design, where precise conditions must be met for desired outcomes.