Which gate outputs true if at least one input is true?

Which gate outputs true if at least one input is true?

• A. AND gate
• B. OR gate
• C. NOR gate
• D. XOR gate

Answer: (B)

The main concept is how boolean gates combine inputs. An OR gate outputs true whenever any input is true, and it stays true even if both inputs are true. This is called inclusive OR. So with two inputs, the output is true for (true, false), (false, true), and (true, true), and only false when both inputs are false. That directly matches the idea of “at least one input is true.” In contrast, an AND gate needs both inputs true, so it wouldn’t always be true when just one input is true. A NOR gate is true only when all inputs are false, which is the opposite of what’s described. An XOR gate is true only when exactly one input is true, so it would be false if both inputs are true.

The main concept is how boolean gates combine inputs. An OR gate outputs true whenever any input is true, and it stays true even if both inputs are true. This is called inclusive OR. So with two inputs, the output is true for (true, false), (false, true), and (true, true), and only false when both inputs are false. That directly matches the idea of “at least one input is true.”

In contrast, an AND gate needs both inputs true, so it wouldn’t always be true when just one input is true. A NOR gate is true only when all inputs are false, which is the opposite of what’s described. An XOR gate is true only when exactly one input is true, so it would be false if both inputs are true.