What is the characteristic feature of a NAND gate?

The characteristic feature of a NAND gate is that it produces a logic "0" at its output only when all inputs are logic "1." This means that the output of the NAND gate will be high (logic "1") for all other input combinations.

To understand this further, consider the truth table for a NAND gate. It shows that the gate outputs a logic "0" exclusively when every input is at logic "1." In all other cases—when any combination of the inputs is low (logic "0")—the output is high (logic "1"). This behavior makes the NAND gate an essential building block in digital electronics since it can create various logic functions and circuits by combining multiple NAND gates.

The other options do not accurately describe the functionality of a NAND gate. For example, stating that it holds a high output when no inputs are high does not cover its specific output condition regarding all inputs being high. Similarly, claiming it produces a logic "1" when all inputs are logic "1" directly contradicts the definition of the NAND gate. Lastly, mentioning that it is functionally similar to an AND gate overlooks the crucial difference in their outputs based on input conditions.