Certain digital logic gate outputs 1 when all inputs are 0. The gate is either

Certain digital logic gate outputs 1 when all inputs are 0. The gate is either:

1. NOR or EX-NOR Gate
2. NAND or EX-OR Gate
3. NOR or EX-OR Gate
4. AND or EX-NOR Gate

Correct answer: 1. NOR or EX-NOR Gate